From Brotato Wiki
Item
Lucky Coin 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.
Lucky Coin
Lucky Coin gives you 2% Luck per Crit Chance you have. The amount changes dynamically as your Crit Chance increases or decreases after you've bought the Coin.
Since Luck is a useful stat for just about every build, the Lucky Coin can be a powerful pickup for any build with high amounts of Crit Chance.