Preheat air fryer to 350°F. Lightly mist the basket with neutral oil.
Whisk flour, sugar, baking powder, salt, and nutmeg in a mixing bowl.
Stir almond milk, melted coconut oil, vanilla, and vinegar in a cup.
Pour wet into dry. Fold just until a soft dough forms; avoid overmixing.
Turn onto a lightly floured surface. Gently knead 3–4 times to smooth.
Roll or pat dough to about 1/2 inch thick. Cut 8 donut rings; re-roll scraps.
Arrange donuts in the basket with space. Mist tops lightly with oil.
Air fry 4 minutes. Flip and cook 3–4 minutes more, until golden and set.
Repeat with remaining donuts. Air fry holes for 3–4 minutes, if using.
For cinnamon sugar: mix sugar and cinnamon. Brush donuts with melted vegan butter; toss to coat.
For glaze: whisk powdered sugar, milk, and vanilla until smooth. Dip warm donuts; let set.