[Gin 'n Tonic]

Worked in supermarket in my youth, guy brings back a Party 7 (a cheap giant can of beer with, I think, 7 pints in it) and complains that it “tasted funny”. The can just had two holes punched in the top for pouring and was mostly empty.

We thought that he was sh*tting us, trying to get some free beer, so we took the can out back and opened it up with a tin opener.

The guy got his refund. Although personally, I would have thought that the ½ a snake that we found at the bottom might have improved the flavour.