See... I couldn't do that to someone. That kind of thing is on my list of 'not even my worst enemy gets that treatment'. Mainly because you can get badly dehydrated and I'd rather not get in trouble for someone's medical issue I may not know about.
It reminds me of this:
I suspect that this isn't real, but anyway: Doesn't this have the obvious drawback that whoever was stealing your brownies knows your name, is very pissed off, and you just handed them a confession to possession of marijuana? Which, I'm guessing from the mention of drug tests and corporate liability, is likely illegal wherever this took place?
Also, re: previous cooment about laxatives: isn't putting a drug (legal or otherwise) in food you expect another person to consume some manner of crime? Arguably poisoning? And, even if not, still disproportionate retribution.
I don't mean to defend the consumption of other people's food, which is an awfully dickish move, but this is the sort of thing that ends with Ron Burgundy amazed at how quickly it all escalated.