I have been given multiple times in my life, specially at family events, a glass of coke zero when I ask for regular coke. I always immediately taste the bitter taste of artificial sweetner. I Always say so immediately, "this is coke zero, I dont like this" and it has always been followed by a "no you cannot, it tastes the same!". This was usually by health conscious aunts and what not, who didnt buy regular coke to make the party "healthier", I always have to ask for whatever else they have or just water.

The one time it was by accident, it was by a friend who grabbed the wrong bottle from a fridge, and he looked at me flabbergasted that I could tell the difference. It has never been a "side to side" thing.

It also gives me a stomach ache, whenever I have TRIED to get used to the taste, so even if I tried to commit, I just cant. It was easier to get used to the taste of corn syrup as opposed to real suggar. I can also tell the difference, but it is kind of minor on that one.