The most common method is setting the player's stamina to 100.0 (or 200.0 for super jump) in a loop. Function: RestorePlayerStamina(PlayerId(), 1.0) is also used.
: For maximum security, check public repositories like GitHub where you can read the code before running it on your server. fivem infinite stamina verified
FiveM-Scripts/basic/infinite_stamina/client.lua at master - GitHub The most common method is setting the player's