Found this recipe on the internet - but haven't tried it myself - sounds interesting....

Coca-Cola cake

I haven’t tried this myself, so I can’t tell if it works or not. But Jane Parks-McKay promises that it’s for real. It’s a reduced-calorie cake made with diet soft drinks.

She says, "Take a favorite cake mix and add only diet soda. Do not put in eggs, milk, oil, water, or whatever. For light-colored or spice cake, mix in diet Sprite. For chocolate or dark-colored cake, use diet Coke. Bake as the directions say, let cool and ice with low/non-fat whipped cream. I tried this for a church potluck and it took care of my sweet tooth without the guilt."

Jane says that you should substitute the same amount of liquid that the mix calls for. If it requires a half-cup of oil and a half-cup of water, for example, use a full cup of soft drink. It’s normal, Jane says, to have a certain amount of "foam factor."