Grease the cups of a muffin tin with cooking spray.
Mix the white sugar and cinnamon in a gallon sized re-closeable bag.
Separate the biscuits, and cut each into 6 to 8 pieces and add to the bag.
Peel, core and dice the apple, and add the apple pieces to the bag. Shake it well to distribute the cinnamon and sugar over the biscuit pieces and apple.
Melt the butter in the microwave, and stir in the brown sugar.
Add a spoonful of the butter mixture to the bottom of 8 muffin cups.
Add the biscuit and apple pieces to the 8 muffin cups and press them down.
Spoon the remaining butter mixture over the top.
Bake for 15 minutes, until the biscuit pieces start to brown.
Invert the muffin tin onto a plate and serve the monkey bread muffins.