Preheat the air fryer to 350°F for 5 minutes and spray the basket with olive oil or coconut oil or use a silicone brush to brush vegetable oil on the bottom. Open the can of biscuits and use a 1 to 1½-inch round biscuit cutter to cut the center out of the biscuits.
Place the donuts on a wire rack on top of a baking sheet (this will catch any dripping butter or excess sugar) and use a pastry brush to brush the melted butter all over the donuts.
Place any leftover donuts in an airtight container for up to 3 days. If you want to enjoy them warm, simply pop them in the microwave for about 10 seconds.