Extra-Strength Bleach
This happened when I was in college back in 2011. I lived in a 4-story dorm that was all guys, about 40-60 guys per floor. Each floor had one laundry room with 3 washers and 3 dryers plus cubbies to store your laundry bag/soap while you were washing.
A few months into the semester I noticed my laundry detergent was disappearing faster than it should be, not a huge deal but mildly annoying. What made it a bigger deal was that whoever was stealing my detergent would also take my clothes out of the washer and leave them on the floor so they could wash their clothes. This pushed me over the line. I would typically do a load while I went to class so this made finding the perp tricky. Then a golden idea hit me.
I went to Walmart and bought a new jug of laundry detergent, the same brand I always get, but I also bought extra strength bleach. I poured half the detergent from the new bottle into my old bottle and replaced it with the extra strength bleach. That next day I did my laundry as usual but left the new and improved detergent in the cubby instead of my regular stuff, then I waited.
After class sure enough my clothes were sitting in a pile on the floor soaking wet and the whole laundry room smelled of bleach, just what I wanted! Fast forward to the next week, every Monday night we had “Floor meetings” where we basically talked about rules and crap as a floor.
In walks the guy, we’ll call him Bob, wearing a newly bleached hoodie and ruined jeans. Bob drops his pile of ruined clothes on the floor and starts spouting off about how “someone owed him money for his ruined clothes.” The whole floor bursts out in laughter; apparently I wasn’t the only one Bob was stealing soap from. He didn’t get another sentence out of his mouth before our RA told him stealing detergent was still a crime so it was his own stupid fault. Enjoy your bleached clothes Bob!
Story credit: Reddit / Pickles_McGee