What is GIVE IT UP FOR DAY 15?

A quote from an episode of Spongebob where the krusty krab stays open for 24 hours. Not knowing how to properly run a 24 Hour restaurant, Mr. Krabs forces him employees and himself to stay awake for days on end, without even allowing them a weekend off. Eventually, they make it to 15 days, and to celebrate, Mr. Krabs rings a bell and shouts GIVE IT UP FOR DAY 15!!!