Preheat your air fryer to 350°F (175°C) for about 5 minutes.
In a mixing bowl, whisk together the flour, 1/4 cup sugar, baking powder, salt, and 1/2 tsp ground cinnamon until well combined.
In another bowl, whisk together the milk, egg, melted butter, and vanilla extract until smooth.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined (do not overmix).
Transfer the batter to a piping bag or a resealable plastic bag and cut a small hole in one corner.
Lightly grease the air fryer basket with non-stick spray. Pipe the batter into the basket in a circular shape, forming your donuts (you can create doughnut rings or round shapes). Ensure they are not touching.
Air fry the donuts for 5 to 6 minutes or until golden brown and cooked through.
While the donuts are air-frying, mix together the 1/2 cup sugar and 1 tsp cinnamon in a shallow bowl for the coating.
Once the donuts are done, allow them to cool slightly before tossing them in the cinnamon sugar mixture until well coated.
Serve immediately and enjoy these delightful air fryer donuts!
Notes
Place the coated donuts on a decorative plate. Optionally, garnish with a sprinkle of additional cinnamon sugar on top and serve with a side of warm chocolate or caramel sauce for dipping.