Yes, you'll need to get a diet pop, as regular pop is sweetened with sugar. Caffeine-free Diet Coke is okay, or Diet 7-up, Diet Sprite, etc. and Diet Mountain Dew. If you can get Diet RC (I've found it in WA), it is sweetened with Splenda rather than aspartame and comes in cola, white grape and a couple of other flavours I can't remember. I've heard of Diet Hansen's as well and Diet Crush (sorry can't remember which flavours) is also Splenda-sweetened.