I usually say "you guys'," but sometimes "you guys's."

The retail-related language construction I love most is "I can help who's next," or sometimes "I can help who's ever next." Back when I worked in a store, everyone I knew said it, and I hear cashiers say it when I'm waiting in line now, but you never hear it anywhere else.

2. God, I wish I knew. I haven't slept through the night in years.