Preheat oven to 350°. Coat a 13x9-in. pan with cooking spray., Beat cake mix, egg whites, water and coconut on low speed 30 seconds. Beat on medium 2 minutes. Transfer to prepared pan. Bake until a toothpick inserted in center comes out clean, 20-25 minutes. Cool on a wire rack 10 minutes., Mix milk and extract. Using a large meat fork, poke holes in cake. Gently spread half of the milk mixture over cake; let stand 3 minutes. Spread with remaining milk mixture; cool 1 hour., Spread with whipped topping; sprinkle with toasted coconut. Refrigerate, covered, until cold, about 4 hours.