Vampires only require blood to survive. They can eat 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 bombard the food causing it to blast into nothing. In the explosive process they disappear as well until a new individual virus replicates. We think this is a good thing because it prevents vampires from eating people rather than sucking blood from them. Of course nothing is stopping them from tearing someone to shreds with their fangs, and bare hands.
Vampires have no appetite for anything but blood. They also don’t have human digestive mechanisms. Most food devoid of blood tastes like nothing to vampires. However they can ingest liquids such as alcohol and water without issues. In fact vampires often partake of alcoholic beverages in between the consumption of blood. Adding alcohol 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. In some cases they might actually eat a few bites to seal the illusion of their humanity to gain acceptance into human groups for nefarious or admirable purposes.