You shouldn't have a problem using gift cards at the snack carts, we just returned from our trip on February 17 and we used Disney gift cards I received for Christmas for things from Dole Whips to Icecream Cookie Sandwiches and bottles of water.
There are some snack carts (not many) at WDW that do not take cards of any type and are cash only. The ones I can think of right now are the outside kiosks at the Boardwalk (like Boardwalk To Go).
There are some snack carts (not many) at WDW that do not take cards of any type and are cash only. The ones I can think of right now are the outside kiosks at the Boardwalk (like Boardwalk To Go).
Now that you mention it, the Funnel Cake Stand on the Boardwalk we needed cash for. We grabbed a funnel cake right before heading back to our room and there was a sign in the window that they only took cash.