I'm gonna be the party pooper here and state that officially, Vlad doesn't drink the blood of his enemies with Q. He steals their life essence. In an early Journal of Justice a summoner asked Vladimir the following:
“I have often chosen
Vladimir as my champion to do battle on the Fields of Justice, and I am filled with a morbid fascination regarding his transfusion...do individual champions have unique tasting blood? Does the dark blood of the Void from, say,
Cho'Gath taste different from the chemical-laden blood of
Singed? Which champion would you say is your ‘favorite’?”
To which Vladimir responded:
The thought of you there, fantasizing about the taste of blood, invigorates me. I do not drink it in the conventional sense; I use it and it fills me. Think of the relationship a cloud might have with water. However, what makes blood special is not its actual taste, but the flavor of the life force which infuses it. That life force is what I ‘taste’ when I use my craft. In this way the blood of Cho’Gath is as different from the blood of Singed as are the two champions themselves. Despite the many flavors, I could not choose a favorite. Variety, like blood, is the spice of life!