Turn your Air Fryer on to 360 degree and preheat for about 5 minutes while you prepare your donuts.
Combine your 1/2 cup sugar and 1/2 TBSP cinnamon in a bowl. Set aside.
Open the can of flaky biscuits and set on a non-stick surface such as wax paper or a silicon baking sheet.Using a 1" round cutter or just any round tool - I used a piece from a pastry bag and it worked just fine - cut a hole out of the center of each biscuit. Set the biscuit holes to the side because you are going to cook those too.
Depending on the size of your Air Fryer, place your biscuits in the air fryer in a single layer and not touching. You will probably have to do two batches. Cook for 5 minutes at 360 degrees. While donuts are cooking, melt your butter in a microwave-safe bowl for about 45 seconds.
When donuts are finished cooking, remove them from the air fryer and place on a plate. Using a pastry brush, brush each donut with melted butter on both sides. Dip into the cinnamon sugar mixture and coat on both sides.
Shake off excess cinnamon sugar mixture. Enjoy these donuts warm.
NOTE: To make the Donut Holes, just pop the holes of the biscuit in the air fryer (not touching) and bake for 5 minutes. Roll in butter and toss in the cinnamon sugar mixture.