The first one says

"I'll have a blood"

so the bartender gives him a blood.

The next one says

"I'll have a blood lite."

So the bartender gives him a blood lite.

The third one says

"I'll have a cup of hot water"

The bartender gives him a cup of hot water and the other 2 vampires look at him with their eyebrows raised and he pulls out a tampon and says

"I'm making tea"