Heat oven to 350. Spray 24 muffin cups w/ cooking spray, lightly. place a pineapple ring in bottom of each muffin cup. Place a cherry in center of each pineapple ring. Sprinkle brown sugar evenly over cherries and pineapples.
In lg bowl, beat cake mix, oil, egg whites and reserved pineapple juice.
Stir in crushed pineapple. Divide mix evenly among muffin cups, 3/4"-full. Bake 20-25 min, or until golden. Cool, invert onto serving plate.