I've been a proponent of the cake mix soda pop idea for many years. I am not sure if this thread is due to wanting to reduce calories in the cake recipe or just because you're curious about the outcome using pop.
My feeling is that the bubbles in the soda pop makes for a lighter cake, as it volumes it up. Plus the extra sugar adds more sweetness to the end result. I love what it does to the OrangeDreamsicle cake.
I wouldn't use diet soda in the cake mix, I mean why would you, seems to be doing nothing for you, as there's sugar in the mix already. I know many who use diet soda in place of water to make their sugar free gelatin.
I would and have used seltzer water and flavored seltzer would work perfectly too.
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