Just look for the purple & white icon. The icon indicates a snack credit eligible ite. You can get everything from ice cream sundaes, Mickey bars, at quick service at resorts look for bakery items. They have large cookies, pastries (using your mug for coffee, tea). Funnel cakes, Ice cream floats. With the holidays look for some speciality snacks (cupcakes).
At Animal Kingdom. Flame Tree BBQ has fries with pulled pork, which is a snack credit.
Quick service restaurants are everywhere. Some of our favorites: La Cantina in Mexico (Epcot). Columbia Harbor House (MK). AK - Yak & Yeti. Flame Tree BBQ. Disney Springs: chicken Guy, Polite Pig and Earl of Sandwich.
If you have quick services lsft, for each credit you can exchange for 3 snack items (if purchased at same time, same location). You can find bags of trail mix, tons of mints, lollipops, chocolate coins and the list goes on at resort gift shops.