If you want chemistry brought into this, then Blast Ph.D. is the guy.

Essentially, I think I agree with what has already been stated. A single beer or stiff drink shouldn't compromise things. It is probably best to use it as purifying agent if there is enough alcohol to make a difference. I am not sure how much "sissy" or regular beer is need to treat a liter of water. Any help from a qualified source(not a Holiday Inn Express frequenter) would help.