Separate biscuits and place them on a cutting board.

Use a bottle cap (or 1" round biscuit cutter) to cut holes out of the center of each.

Optionally, grease air fryer basket with olive oil.

Place 4 donuts in a single layer in the basket, making sure they aren't touching.

Cook at 370 for 5 minutes, flipping halfway through, until lightly browned.

Mix together sugar and cinnamon in a shallow dish.

Remove donuts and dip in the melted butter.

Place in cinnamon sugar mixture, turning to coat evenly.

Repeat with remaining donuts.

Serve warm.