A guy's in his car with a girl and says, "How about a hand job?"

She says, "What do I have to do?"

He says, "Remember when you were a kid and you used to shake up a Coke bottle and spray your brother with it? Just do that."

She grabs it and does it. A few minutes later, he starts screaming. She says, "What's wrong?"

He says, "Take your fucking thumb off the end."