Preheat the air fryer: Set to 350°F (175°C) for a few minutes. Lightly spray or brush the basket with oil so the donuts don’t stick.
Prep the biscuits: Open the biscuit can and separate the dough.
Use a small round cutter, bottle cap, or piping tip to punch a hole in the center of each biscuit. Save the cutouts for donut holes.
Arrange in the basket: Place biscuits in a single layer with space around each one. Work in batches if needed—crowding leads to uneven cooking.
Air fry: Cook the donuts for 5–7 minutes, flipping halfway.
You’re looking for a deep golden brown edge and a lightly puffed center. Donut holes take 3–4 minutes total.
Make cinnamon sugar: While they cook, mix 1/2 cup granulated sugar with 1–2 teaspoons cinnamon in a shallow bowl.
Make classic glaze: Whisk 1 cup powdered sugar with 1–2 tablespoons milk and 1/2 teaspoon vanilla until smooth and pourable. Add a splash more milk if it’s too thick.
Coat the donuts: As soon as the donuts come out, brush or dip them lightly in melted butter.
Toss in cinnamon sugar or dip tops in glaze. Add sprinkles or chocolate while the glaze is wet.
Serve warm: They’re best fresh, when the edges are crisp and the centers are soft.