Heh, you want to experience hallucinations without drugs? I say go without sleep for a night or two, spin around in a circle 20 times real fast. Quickly sit down on the floor(still dizzy and tired) put your head to the floor and then raise your head up as fast as you can where you fall back to the floor and lay there staring at the ceiling.. It will lead to some forms of hallucinations if you do it just right..
NOTE: Hallucinations arent something really great to experience, maybe once or twice wont bother you but I have a strange case of paranoid schizophrenia, I get hallucinations pretty much everyday without drugs, and they arent something I would want you to have in your life.