The Main Street Bakery in MK let us get 2 pastries and a drink for either 1CS credit or 3SC. We got 2 of the gignormous cinnamon rolls on the way out of the park at the end of the night to save for an in room breakfast the next day, along with a bottled drink that we usually shared right away. I used both CS and SC during our stay for this, since we had a few extra CS credits toward the end of our stay.
Your resort food court or grab & go is the best place to ask though, more success reported there than in the parks in using CS credits for snack items.