From Brotato Wiki
Item
Cute Monkey is an in-game item that can be bought from a Shop or can be found in a Crate. Most Items modify the Stats of the player, and some of them provide additional effects.
Scaling
Multiple Cute Monkeys are Additive. So 2 Cute Monkeys give 16% chance to trigger for 1 HP. And 5 Monkeys gives 40% and so on.