So you want to make someone's life be 'down in the dumps' so to speak? There are many many things that can do this, mostly food orientated. Castor oil doesn't taste very good, but it will do the trick, coconut milk in a big enough quantity (like 1 or two full glasses), coffee to some, watermelon, and lots of alcohol to name a few. And there is always the classic standby in today's modern era. Chocolate laxatives. Bake some real good brownies with those and your intended will be spending quite some time on the porcelain throne.