Vampires only require blood to survive. They can eat regular food but even a small portion acts as a mild poison. It weakens them, and too much food can actually render them unconscious for hours. During this time the food actually disintegrates into nothingness inside their body by supernatural means. Scientific analysis indicates that the individual vampire viruses that become apart of their cells swarm the food devouring it in lieu of the vampire. Within them the food is quickly vaporized by taking it apart at the metaphysical energy level. In the explosive process the portions of the virus attacking the food disappears as well until a new individual virus replicates. This is why they get weak after eating. We think this is a good thing because it temporarily prevents vampires from sucking blood from people. A common Vampire Slayer tactic to weaken vampires is to taint blood supplies with particles of food. Things such as garlic, or silver might be detected before they ingest it.
Vampires have no appetite for anything but blood. They also don’t have human digestive mechanisms. Most food tastes like nothing to vampires while blood is the sweetest of nectars. Interestingly enough they can ingest alcohol, and water without issues. Since their is water in their bodies it is absorbed into their tissues. This includes alcohol which is mostly water. The other ingredients don’t strain the vampire virus.
Vampires often partake of alcoholic beverages in between the consumption of blood. Despite not being able to get drunk they can experience something like drunkenness when gorging on insane amounts of blood. Far more than the vampire virus can digest. Adding alcohol,or blood to food brings out the flavor so they can at least taste it in their mouth for the experience before spitting it out. In order to fit into human social situations they will pretend to eat food, and then discreetly use a napkin to get rid of it. However when food is doused adequately in alcohol or blood they can ingest more than usual without getting noticeably weak. The only reason to eat food is to seal the illusion of their humanity to gain acceptance into human groups for nefarious or admirable purposes.