Coca-Cola Classic and Coke Zero contain flavoring agent from the cocoa plant.

“And to this day, uh, Coca-Cola Classic and Coke Zero are the two products. Interestingly enough, um, you know, Diet Coke does not taste very much like Coca-Cola original. And a lot of people complained about that for a long time. Um, they got smart and made this product called Coke Zero that has the flavoring agent from the cocoa plant in it. And lo and behold, everyone started saying, "Gosh, this tastes a lot more like Coca-Cola does." Well, yeah, it's got the flavoring ingredient in it.”