From Brotato Wiki
Adrenaline is an in-game item that can be bought from Shop or can be found in a Crate. Most Items increase the Stats of the player while some of them provide unique effects.
Adrenaline is a unique item. Unique items can only be bought or found once per run.
Adrenaline has 50% chance to provide you with a 5 heal when you dodge an attack. This can be a powerful way of healing if you have the maximum amount of dodge, 60% or close to that amount. This can be especially useful on Melee builds that are more likely to get hit often such as Brawler's fist build. The Character Ghost can reach up to 90% dodge chance, making Adrenaline a powerful option for healing.