Make cake mix according to package directions, using water and egg whites, bake in a 13”x9” baking pan. Cool on wire rack. Cut half the cake into 1” cubes (freeze or reserve remaining cake for another use). Process strawberries in blender or food processor until smooth; stir in sugar substitute. Layer 1/3 of the Milk Custard and strawberry puree over cake and top with 1/3 of the raspberries, nectarines, bananas, and blueberries. Repeat layers 2 times. Refrigerate at least 1 hour before serving.
Garnish with whipped topping. Makes 12 servings.