Preheat oven to 350°F (175°C). Generously grease a Bundt pan or 9x13-inch baking dish.
Cut each biscuit into quarters. In a large bowl, mix granulated sugar and cinnamon. Toss biscuit pieces until evenly coated.
Chop apple pie filling into bite-sized pieces.
Layer half of the coated biscuit pieces in the pan, then spoon half of the apples over the top. Repeat with remaining biscuits and apples.
Stir melted butter and brown sugar until smooth. Pour evenly over the layered biscuits and apples.
Bake for 35–40 minutes until golden brown and cooked through. Loosely cover with foil if browning too quickly.
Cool for 10 minutes, then carefully invert onto a serving plate. Whisk confectioners’ sugar and milk and drizzle over warm monkey bread if desired.