We were on
DDP in April. Snacks were the most confusing part of the Dining Plan. Every place we went to seemed to vary. For instance Minute Maid frozen lemonade was on the DDP at Epcot, but not at Typhoon Lagoon. Something that was a snack at one place, wasn't at the other!
I found the best thing to do was ask a CM NICELY. "We are on the
Disney Dining Plan and would just love one of those Sugar Cookies for a snack, would that be possible?". We were able to get some things that were probably not normally considered snacks, just by being friendly and asking nicely. It didn't work all of the time, but sometimes it did!
Have a Great Trip!