That happened to me!
Wifey drinks the Diet (no; it AIN'T working) and I the regular.
I accidently gave her one of mine to take to work.
She was NOT happy - said it tasted like battery acid. (She got that from me when I sip HER stuff!)
I hadn't realized how close the labels were, as Coke® is ALWAYS doing something to their cans.
My sis sometimes gets ribbed for drinking a Diet Coke with a candy bar, as if she is supposed to be thinking the diet drink "cancels" the candy. But the fact is, she drinks Diet Coke for the taste, not for the "diet".