20 dollars

Two men are in a bar getting drunk. Suddenly one of them throws up all over himself.
He says "Oh, no. Now my wife will kill me".

His friend says "Don't worry. Just tuck a twenty dollar bill in your breast pocket and tell your wife that someone threw up on you and gave you twenty dollars for the dry cleaning bill".

So they stay for another couple of hours and get even drunker.

Eventually he reels home and his wife starts to give him a bad time.

"You reek of alcohol and you've thrown up all over yourself, my God you're disgusting" etc.

Speaking very carefully so as not to slur, he says, "Wait. It's not what you think. I only had one drink, but this man was sick on me. He'd obviously had one too many, or else he just couldn't hold his liquor. He was very sorry and he gave me twenty dollars for the cleaning bill. Look in my breast pocket."

She looks in his breast pocket and says, "But this is forty dollars".

"Ah, yes." says the man. "He pee'd in my trousers too".