>>212532901
Just eat a cup of mashed up apple seeds.
Apple seeds all contain a miniscule amount of naturally occurring cyanide. But it's located within the center of the seed, so you'll have to mash them up with a mortar and pestle.
With cyanide poisoning you'll be dead in a manner of seconds. Well, either that or the dose will be insufficient to kill you and you'll be in the worst pain you can possibly imagine, but hey, no risk no reward, amirite?