Food contamination and potentially spreading diseases are not worth the bittersweet revenge of watching a rude customer gag, but the rage caused by someone belittling your entire sense of self and human existence over their missing free-refill of soda is definitely strong enough to fuel some dreams about it.
So, when a Reddit user asked restaurant workers, "what is the worst thing you have seen done to a customer’s order?" people with secret stories from the kitchen were ready to spill the nasty details.
If you were a d*ck I guaranteed your bread was over toasted, the lettuce on your sandwich was wilted, the tomato was the butt end with the hole from us removing the core, your onions were little pieces, the meat was the smallest of the portions, and on and on. I wouldn't tamper with someones food but I damn well wasn't making them a good sandwich.