Lay the biscuit dough on a flat surface, like a cutting board. Use a cookie cutter or a small shot glass to cut holes in the dough.
Lightly grease the air fryer basket with some cooking oil.
Place the donuts (and/or donut holes) in the air fryer one at a time and ensure they aren’t touching each other.
Cook the donuts at 350 degrees for 4-5 minutes or until they are golden brown.
As the donuts are baking, fill a medium bowl with the granulated sugar and cinnamon; mix everything together with a spoon.
Once the doughnuts are done, remove them from the air fryer using a pair of tongs and brush them with the melted butter using your pastry brush. Once the donuts are coated in butter, brush them with the sugar and cinnamon mixture.