Real simple. Simply crouch on the ground and take deep breathes for at least 30 seconds, then stand up rly fast stick your thumb in your mouth and try to blow on it rly hard. The result: you pass out for about 3-5 seconds!!!
Note: have a friend catch you or make sure you have something soft to land on lol! You don't do any lasting damage but dont do it too often or you will get a headache