Preheat your air fryer to 350°F (175°C) for about 5 minutes.
On a clean surface, open the biscuit dough and separate the biscuits. Use a small round cutter (or a bottle cap) to cut a hole in the center of each biscuit to form a donut shape. Reserve the holes to fry them as donut holes.
In a small bowl, mix the granulated sugar and ground cinnamon together. Set aside.
Dip each donut and donut hole into the melted butter, coating them well.
Roll the buttered donuts in the cinnamon sugar mixture until fully covered.
Place the coated donuts in the air fryer basket in a single layer, making sure they don't touch each other. You may need to cook in batches depending on your air fryer size.
Air fry the donuts at 350°F (175°C) for 5-7 minutes or until they are golden brown and cooked through, flipping halfway for even cooking.
Remove them from the air fryer and let them cool slightly on a wire rack. If desired, dust with powdered sugar for an extra sweet finish.
Notes
Optional: dust with powdered sugar for an extra sweet finish.