I guess there's a lot of people out there who don't understand the word Reciprocation.
I had a 6 pack of soda in the fridge at my barn and one day I know it's my last one and would you believe someone drank half of it and put it back in the plastic ring!
This is what I would do and I've done it.
Make a nice sandwich and put a nice schmear of toothpaste in it or anything safe that taste gross that won't make them sick.
Load your cold drinks in containers with salt .
Refill your coffee creamer with flour if powder or mix in something like garlic...