Open biscuit dough. Separate biscuits.
Cut each biscuit into 4 pieces (32 pieces total).
Mix sugar and cinnamon in small bowl.
Brush each piece with melted butter on all sides.
Roll each buttered piece in cinnamon sugar. Coat completely.
Preheat air fryer to 350°F for 3 minutes.
Spray basket or line with parchment paper.
Arrange pieces in single layer with gaps between. Work in batches.
Air fry at 350°F for 6 to 8 minutes until golden. Check at 6 minutes.
Remove. Cool 2 minutes.
Make icing. Whisk powdered sugar, milk, and vanilla until smooth.
Transfer bites to serving plate.
Drizzle icing over warm bites.
Serve immediately while warm.