There's a link that has confirmed snacks
http://disboards.com/showthread.php?t=1683477 but it doesn't show anything
confirmed for 2008 for either park. Someone has to report to that thread what they have gotten using a SC before it gets posted.
I know you can't use them for the mini donuts.

I can't remember if you can even charge them to your KTTW card.
I think most of the smaller food locations can't use the KTTW cards. (therefore no DDP credits either ) When we've gone to the waterparks we've only used our DDP to get lunch (inc. dessert). You can return later in the day to get your dessert (ice cream). One park give you a token, the other one makes a tear on your receipt once you get your ice cream.
In Sept. 06 I took a pix of the sign at Typhoon Tilly's at TL. You can see the symbols next to the items that were considered snacks then. (don't know if you can still get them in 2008)
You can see they had several options besides ice creams. I think Typhoon Tilly's and Leaning Palms at TL, and Lottawatta Lodge at BB are your best possibles for using SC.
Hopefully someone who's been in 2008 can confirm some snacks at TL and BB so they can be added to the list.
HTH.