She has a reputation for being 'good/great in the sack'. [=for being a good sexual partner]
He's ready to 'jump/climb in the sack' [=have sex] with any woman who'll have him.
The company 'gave him the sack' [=fired him] for improper conduct.
(..) so I'm thinking they can take us. And so I, uh, heh... I just heave it downfield. What are you, crazy? That's a baby. He should take the sack? Anyway, suddenly I'm downfield. And I realize that I'm the one who's supposed to catch him, right? Only I know there's no way (..)1995 TvShow: Friends Title: The One with Two Parts: Part 2 Season: 1 Episode 17