I could be a smartass and say my own saliva, since we really do that all the time... but that'd be stupid.
hasn't anyone said coffee yet? that was my last drink. Had spent several hours in a thermos bottle though, yuck.
btw, coffee is only the drink if all that's added to it is any mixture of cream, sugar and milk. white chocolate mocca and that coffee-flavored sweetened milk don't count.