I purchased a few cans of cider in Superquinnn a couple of years ago and they wouldn't scan. The guy on the till said "you get them for free so do you want to get a few more"!
The he tells his mate who had just clocked off and was on the way home so he goes and gets a rake of them for free.
The cans didn't scan the next week either and got them for free again.
They had none left the following weekend.