that depends - are you dieting for a show? if you are, you might not want to hinder the fat loss.
if it's just for those two nights and you're not on any kind of aas, i don't see why you couldn't have a bit of a splurge. it won't effect your muscle significantly in that short of a period of time.
i'm not sure why you mention water - the dehydration factor? if you prefer to remain hydrated, drink lots of water as well as the booze.