Heat oven to 350°F. Peel apples; grate them into a medium bowl. In a small bowl, combine sugar and cinnamon. Stir half of cinnamon sugar into grated apples.
Roll each biscuit to about a 5-inch circle. Spoon apple mixture onto circles. Fold circles over and pinch edges to make half-moons. Place on a baking sheet.
Brush pies with water and sprinkle with remaining cinnamon sugar. Bake 20 minutes.