1. Heat oven to 375 degrees F.
2. On a flat surface, stack phyllo sheets, lightly coating the top of each with butter-flavored cooking spray. Cut in half; put one half on top of the other to form a stack of 6 layers. Cut into 6 portions (about 4 1/2 inches square).
3. Bake for 10 minutes, or until golden brown. Allow to cool on pan on rack. Preheat oven to broil.
4. Mix sugar and cinnamon in bowl; set aside.
5. Arrange apple slices in two 9-by-13-inch baking pans. Lightly coat slices with cooking spray. Broil for 1 minute. Stir. Sprinkle with cinnamon sugar. Broil for about 1 minute.
6. To serve, top each phyllo stack with apple mixture and frozen yogurt.