Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 9 inch round cake pans.
Combine cake mix, water, oil and egg whites and beat for 2 minutes until blended. Fold in sprinkles. Pour batter into prepared pans. Bake in the preheated oven for 35 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow cake layers to cool in pans for 30 minutes.
Frost cake layers with whipped topping and assemble on platter. Cover top of the cake with as many chocolate candies as possible, and surround the bottom of the cake with remaining candies.