This is from a dialogue in The Round House by Louise Erdrich. Huge spoiler ahead, so be warned if you haven't read the book.
Joe and Cappy, who are 13 year olds, drink a half quart Four Roses which was given to them by Joe's uncle Whitey. After they finished drinking and about to leave Whitey to go to their parents, Whitey says:
Gimme your shirt, Joe, he said. Leave it here. Touch the bottle again. You, too, Cappy.
Joe and Cappy have killed a man only a couple of hours ago and both puked. I'm guessing they have puke in their shirts, and since Whitey knows they committed a murder, he doesn't want their parents to know anything is out of the ordinary with them. But I didn't understand why they had to touch the bottle again.