Random Riddle: 9-23-2012

Blood, he's a vampire!
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A man goes out drinking every night, returning to his home in the wee hours of every morning. No matter how much he drinks, he never gets a hangover. This drink is very well known, but is rarely consumed, served warm and taken straight from its source. The man is a sucker for a free drink, especially since he can’t live without it.

What is his favorite drink?