Unlike most techniques, Sleep is a basic biological function of most living beings (including Humans, Saiyans, Majins, and most alien races) and, as a result, it is one of the few techniques that can be used by anyone regardless of power level (even untrained persons like Bulma).
Appearance in games
In the Budokai Tenkaichi games, the technique is used by Grandpa Gohan, Great Ape Kid Goku, Great Ape Raditz, Cui, Frieza Soldier, Goten, Majin Buu, and Kid Buu. The character falls asleep for a few seconds, during which they are very vulnerable to attacks. If it is successful, the character's health and ki will recover substantially, along with adding all stat bonuses.
In Dragon Ball: Xenoverse, it is called Quick Sleep and is a Super Skill that allows the user to gradually recover health for as long as they remain asleep. It appears as one of Kid Buu's Super Skills in his 1st skillset. It can be also be obtained by the Future Warrior as a reward in Parallel Quest 41: "Frieza's Nightmare Returns!", however it is can only be used by the Future Warrior if they are a Majin.