1 (18.25 ounce) package white cake mix
2 1/4 cups instant breakfast mix
2 1/2 cups milk
3 egg whites
2/3 cup white sugar
2 tablespoons water
1 1/2 teaspoons vanilla extract
Preheat oven to 350 degrees F (175 degrees C). Line bottom of preheated oven with foil. In a large bowl, beat together cake mix, instant breakfast mix, milk, egg whites and sugar. Add 2/3 cup water and milk; mix well. Stir in vanilla extract.
Divide batter evenly among prepared 9x5 inch pan. Line pan with foil.
Bake, uncovered, for 40 to 50 minutes. Let cool. Using a long serrated knife, cut down to center of cake several times to remove from foil. Make several small cutouts with pastry bag or 1/4 cup fork, leaving 3 inches from the pan. Using a knife, cut slices into 1 inch from the bottom of the cake. Cool completely before serving.