While Granny Smith is a classic variety that's all the way on the tart side, other apple types can work, too. Go for an apple that's firm. Soft apples mush when cooked, which makes them better suited for things like Instant Pot applesauce. Other firm apples that would work here are Pink Lady and Honeycrisp. If you'd like to use up apples that are on the sweet side (Fuji, Gala - perfect for air fryer apples), you may consider slightly decreasing the amount of brown sugar used to coat the apples.