Preheat the air fryer: Set it to 350°F (175°C).
Lightly coat the basket with oil spray to prevent sticking.
Mix dry ingredients: In a medium bowl, whisk 1½ cups flour, 2 teaspoons baking powder, ¼ cup sugar, ½ teaspoon salt, and ⅛ teaspoon nutmeg.
Mix wet ingredients: In another bowl, whisk ½ cup milk, 3 tablespoons melted butter (slightly cooled), 1 egg, and 1 teaspoon vanilla.
Combine: Pour wet into dry and stir gently until just combined. If the dough seems sticky, add a tablespoon of flour at a time until it’s soft and scoopable, not wet.
Shape the balls: Use a small cookie scoop or spoon to portion 1 to 1½-tablespoon mounds. Lightly oil your hands and roll into smooth balls.
Air fry in batches: Arrange donut balls in a single layer without touching.
Lightly mist the tops with oil. Cook 6–8 minutes, shaking the basket halfway. They’re done when golden and springy to the touch.
Coat with cinnamon sugar: Mix ½ cup sugar with 1 teaspoon cinnamon.
Brush warm donut balls with melted butter and roll in the mixture. Work while they’re warm so the coating sticks.
Or glaze: Stir ¾ cup powdered sugar with 1–2 tablespoons milk and a few drops of vanilla until smooth. Dip warm donut balls, then set on a rack to let the glaze set.
Serve: Enjoy warm.
They’re best within a few hours but still tasty later with a quick reheat.