All blood is drinkable if you want to be technical, though not everything will be a good "meal."
The following are races that Vampires can actually find nourishment from, ranging in levels of nourishment.
The deep ones: Medium.
Vampires can -try- to feed from anything, and the following is a detailed list of effects of certain kind of blood in Ascension City.
Drinking from another vampire is often a sacred and intimate exchange of blood between friends, family, or lovers. Sharing blood for longer than a month produces a stronger bond between two vampires, whether symbolically, or psychically to a small extent. When a vampire they are bonded with is within fifteen meters of them, even a person without aura perception may sense their presence or have a vague idea of one thought or feeling (consent based). While vampires are cold, room-temperature, beings...drinking from a creature of the same temperature is warm, and the taste is as marvelous (or at least the mind triggers it to seem so) as siphoning a small portion of the energy of the other vampire's essence. No nourishment is gained aside from emotional or mental peace, enjoyment, or invigoration...depending on a feeding being forced or not. Often times drinking vampire blood while in a frenzied state can bring some level of calm to the wild vampire.
Incubus/Succubus: Demons who are of the incubus variety often secrete pheromones from their body that induces lust. While a vampire is not fully immune to these pheromones, when these types of demons are bleeding or they ingest some of their blood, most are overwhelmed with sexual desire and suffer from a strong, pleasurable, tingling sensation through their entire body quite like tasting red sugar.
Other demons: Drinking from a demon is similar to drinking from a vampire, simply from the connection they have from the creation of the vampire race. Drinking from a demon has a strong, indescribable taste that some vampires either find to be fully invigorating...or completely intolerable. For either flavor, it is a highly addictive acquired taste. Once a vampire develops a taste for it, they will need solitude and therapy to conquer the addiction.
-Blessed: A blessed Earthborn -while pleasing to the taste- is about the same as drinking Oregano oil straight up. It burns on the way down, in an extremely painful and disorienting way. The energy of their faith in their divine and blessings bestowed upon them for their ethereal purpose to Gaia make drinking their blood as pleasant as a wine-drenched cross shoved down one's throat.
-Cursed: While contrary to some popular belief, the cursed Earthborn are barely as tolerable as their blessed relatives. With the faith they invest in serving Hades, that energy is sometimes insufferable to the taste and makes their blood taste incredibly bitter and often sour and rank. While they may gain some small level of nourishment, its so counteracted by how ill it can make a vampire that there is really no benefit to drinking from one.
Djinn: Drinking from a Djinn is about the same as drinking a glass of water. For some reason it is devoid of flavor and light over the tongue because of the Djinn being a spirit creature. If there is a flavor, its only a vague aftertaste of whatever happens to be on a Djinn's skin. The equivalent of airy rice cakes, no value whatsoever besides the feeling of something being in the mouth.
Elementals: Drinking from an elemental depends entirely upon the type of elemental involved. However, most elementals have such a plant-like, bland, or tasteless flavor that there is little point in drinking from them. The only exceptions to this are Shadow Elementals and Necromentals. Because of the shadow elementals being so similar to the energy produced from the New Moon, a vampire could gain a mild bonus of strength towards one ability for a few hours, while drinking from a necromental in any way is the same as drinking from any of the true undead races. It will make a vampire bedridden for several hours to the remainder of the day, and tastes very rank and sour.
Familiars: Pleasant, succulent, and nutritious to a vampire. They taste the same in human or animal form, and so a vampire might notice the variances in flavor while partaking of one in human form.
Skinwalkers: These shamanic humans taste similar to mixing animal blood and incense and trying to swallow the concoction. It may resemble an animal, but the mild burn to the liquid generally deters vampires from enjoying the subtle hints of a smoky flavor. While it is not an unbearable burn, most cannot stomach the unpleasant taste of potent spices caused by the faith they invest in their totems. What can I say, some vampires like it spicy.
LYCANS & SHIFTERS
Were-creatures and shifters: Perhaps in part of the creation of Lycans being rumored to have been crafted from a rite of passage concerning the Ascension Stone, there are almost no nutrients in a Were's blood that can be harvested regardless of a were having a human form. Drinking can nourish to a degree; however, if there is any essence in the blood that is consumed the result leaves a vampire in an aggressive, tense, or primal state. Those with a frenzy weakness should avoid the risk of drinking a great deal from a were creature, if at all possible. Not to say they enter into an uncontrollable frenzy, but their judgment will be impaired for several hours, and the wrong thing said around a person could issue a fight or brawl from a normally calm-spirited vampire. Only has a strong risk of this happening if one quart of blood or more is ingested. About as addictive a substance as caffeine, with a mild smoky flavoring.
Primal: Drinking from a primal is like drinking heavily concentrated werewolf blood, and it can take very little to cause a vampire to have impaired, often aggressive or violent, judgment. Drinking one quart from a primal can sometimes make a vampire act on animal urges...such as trying to drink from another person in the street or sexually mount someone. The potent smoky flavor has no burn, but it can become an addictive substance if a vampire continues to have small doses of it over the course of a month, but not to the same degree as demon blood.
Merfolk: As far as biting into a merrow being, often times around the fangs it can feel similar to biting into cooked salmon, with a similar succulent flavor to tantalize the senses. After drinking from a mermaid, the vampire is mildly susceptible to being influenced or advised in one way. As though mildly under the effects of a siren's song.
Nightmers: Drinking from a nightmer is similar to the consistency of drinking from their cousins the merfolk...except in the process of consuming the blood it will feel as though mental strength and one's spirits have been psychologically drained in some way. One may leave with a full and happy stomach, but feel so weary and tired psychologically that the dinner might make a vampire feel worse than before they dined.
The deep ones: As far as this unique aquatic race goes, the flavor of the being can vary depending on whether the Deep One has reached the age of transformation yet. Before this time, they may taste so much like a human that the average vampire may not recognize a difference. After a Deep One has reached the age of transformation and is in human form, the taste will have a mild seeweed-like aftertaste to what seems like human blood. An acquired taste to most vampires, though for those who don't know what they're tasting, they may think the human is just sick and avoid drinking from them.
Encantados: Drinking from an Encantados tastes and feels very similar to drinking from a merrow or merfolk, in that it leaves the vampire feeling in higher spirits and more susceptible to being influenced in some way. The flavor is slightly sweet and savory, as opposed to just savory, and is considered to be a rare delicacy even though no nutritional value is gained.
Selkies: Drinking from a Selkie is an enriching experience, not just for the savory flavor, but because of the strength of longing that burns in the soul of a vampire who drank Selkie blood. Often times a vampire may feel a strong pull of some sort, either towards the new moon, or to the ocean, where one ordinarily wasn't there. Its rather mystifying, and if more than a quart is consumed, they say its like drinking from the soul of the sea.
Atlanteans: Drinking from an Atlantean, while there is no physical nutrition given, is rumored to produce an hour or two of increased clarity. A vampire who may not be the brightest crayon in the bunch may understand jokes, riddles, or problems that they might not ordinarily comprehend. Taste-wise, Atlanteans have a tangy flavor that lingers on the tongue even after the clarity dissipates.
BEASTS AND MONSTERS
Mundane animals: Mundane animals are not very nutritious at all, and viewed as a "last resort" and pitiable offense by most vampires. Animals can vary in how they taste depending on the animal one tries to drink from.
Bogeymen: Drinking from a Bogeyman is about the same as drinking a glass of water. For some reason it is devoid of flavor and light over the tongue similar to a Djinn. If there is a flavor, its only a vague aftertaste of whatever happens to be on a Bogeyman's human-facade skin. The equivalent of airy rice cakes, no value whatsoever besides the feeling of something being in the mouth. But that is just the flavor and consistency...in the moments immediately following the first swallow of Bogeymen blood, the vampire is rendered with an unexplainable and intense fear that -depending on how much blood is consumed- will render the vampire either still or paralyzed completely in a state of terror.
Trolls: For those foolish enough to try and overtake a troll, the blood is bitter with a earthy quality that sometimes tastes similar to garden soil. Given the thick, syrupy texture -whether imagined or not- the blood is usually not very pleasant to consume, and often makes a vampire feel sluggish for about an hour or thirty-minutes after feeding.
Goblins: With trying to drink from a goblin, there is a mild risk of infection. While vampires are generally immune to all diseases, there is something about drinking the blood of a Goblin who has viral saliva that can riddle a vampire with stomach cramps or nausea. For those who drink from a normal goblin, the consistency of the blood is 'interesting' and a bit strange to swallow from the almost syrupy texture left on a vampire's tongue. Like drinking old licorice in liquid form.
Minotaurs: To any vampire daring enough to try and feed on such a fierce creature, Minotaur blood has a very succulent flavor and texture. However, in most instances the minotaur catches the vampire and deals to them a strong beating as punishment for the attempt, which is not exactly the type of rodeo that would be wise to gamble one's body with.
Gargoyles: Vampires, even with having stronger and sharper teeth than a human, usually can't bite into a gargoyle in order to partake of their blood. Even in their moveable forms, they do have very tough skin that is uncomfortable to pierce through. Its a bit too much effort usually for the bland, off-color, blood found within.
Intolerable and toxic, drinking too much blood from a truly undead race will riddle a vampire with sickness and often make them bedridden for several hours.