Prepare cake mix according to directions, using a 2 egg carton of egg substitute if desired. Bake in two 9 inch round layers; split layers horizontally when cool to make 4 layers.
Blend together sugar, sour cream and coconut and chill. Spread all but 1 cup of this mixture between the layers. Blend the remaining cup of mixture with the whipped topping and spread on the top and sides of the cake. Seal cake in airtight container and refrigerate for at least one to three days before serving.