Substituting Sparkling Water for Soda in Diet Cake?

I am going to be making a diet cake (or maybe you call it soda cake) soon. I want to know if instead of the can of soda, if I can use 12oz. of sparkling water? It is flavored, carbonated water, so pretty much like diet coke. Would this turn out the same? For those of you who don't know, you just mix a can of soda with a box of cake mix and bake. It's delicious.

By Becca25 from NY