In a large bowl, whisk the sugar and oil together for 1 minute, until lightened and glossy.
Beat in the egg and vanilla until fully combined.
Add the flour, baking powder, baking soda, salt, and cinnamon. Mix just until the flour disappears — do not overmix.
Fold in the diced apples, cranberries, and walnuts by hand.
Grease three mini loaf pans with butter or non-stick spray. Divide the batter between them, filling each two-thirds full.
Place the pans in the air fryer basket or on the lowest rack. Air fry at 320°F for 20 to 25 minutes, without opening for the first 15 minutes.
Test with a toothpick in the center of a loaf. It should come out clean or with dry crumbs. Add 3 to 4 minutes if needed.
Cool in the pans for 10 minutes, then turn out onto a rack. Cool at least 20 minutes before slicing.