How to make laxative brownies?

I've had some problems with coworkers, I'm not saying I am a saint, but I'm not saying I'm the devil reincarnated. However they are constantly putting food (for example raw onions, fried chicken) in my hoodies. I don't like that, I would never ever do that to someone because it's disgusting. I should explain I'm a bit OCD which everyone knows, its not a secret. I've tried telling my boss but he laughs and doesn't do anything because he knows they would probably make my life a living hell. Oh by the way I work in a restaurant so food is at there disposal all the time. I would really like to get even with them and make some laxative brownies so I can have the last laugh but I don't want to hurt them. They are hungry for anything that's not made at the restaurant. I've made food in the past and brought it in (before all the leftovers were discovered in my hoodies,) so I figured food would be the best way to get even.