Whenever we are at our favorite place with free flow of drinks, my son will go fill up our paper cups and I'd always ask, you sure this is Coke Zero? 

And he'd just give me that look. 

But when I didn't ask him that question today was when it mattered. 

He drank it and said, "This is not Coke Zero." 

Apparently, it was switched between the two and I drank half a cup of sugar-filled drink. 

pearlie