1. Heat oven to 350°F; grease 13 x 9 x 2-inch baking pan. Prepare cake mix according to package directions, using 1-1/3 cups cola in place of water and stirring 1 tablespoon grated orange peel in batter. Pour batter into prepared pan. Bake 30 minutes until wooden pick inserted in center comes out clean. Invert cake onto wire rack cool completely. (Cake may be made and stored, tightly wrapped, up to two days before decorating.)
2. Stir chocolate chips in small heavy saucepan over very low heat until melted and smooth; remove from heat. Dip strawberries into chocolate to coat halfway, placing each berry as it is dipped on cookie sheet lined with wax paper. Refrigerate berries until ready to use.
3. Cut cooled cake horizontally into 2 equal layers with sharp serrated knife; place bottom layer on large cookie sheet.
4. Beat butter in large bowl with mixer at medium speed until light and fluffy; gradually beat in confectioners' sugar and chocolate drink mix until smooth. Beat in 1/3 cup of remaining cola, remaining 1 tablespoon grated orange peel and vanilla until thoroughly blended and smooth. Spread half of frosting over bottom cake layer; top with second layer. Swirl remaining frosting over top of cake. Cut cake into 12 portions; arrange on platter. Decorate with chocolate-dipped strawberries, if desired.
Note: For firmer cake, use one 16 oz. package of pound cake mix, stirring in 1/3 cup powdered chocolate drink mix along with grated orange peel. Use cola for the liquid; bake as directed.