Preheat oven to 350 degrees. Mix water, egg whites and cake mix in a large bowl at low speed for 30 seconds. Increase speed to medium and beat for 2 minutes. Pour batter into a 13x9x2 inch baking dish that is coated with non-stick cooking spray. Bake for 35 minutes or until cake springs back when touched lightly in the center. Let cool in pan on a wire rack.
Beat milk and pudding mix in a medium bowl at low speed for 2 minutes or until thickened. Cover and chill for 5 minutes. Stir in pineapple. Using handle of wooden spoon, pierce 48 holes in top of cake. Spread pudding mixture over cake and spread whipped topping over pudding mixture. Toast coconut in flat pan for 7 to 10 minutes, stirring frequently for even toasting. Sprinkle topping with toasted coconut. Refrigerate.