The night before baking the cake, combine sugar, sour cream and coconut. Store in the refrigerator. The next day prepare the cake and bake in 2 (9 inch) layers by package directions (350 degrees for 25 minutes). Invert cake; cool. Split each to make 4 layers. Fill and frost with sour cream mixture. Refrigerate; don't cut for 3 days; even better to leave for 4 days. Keep in cake box, covered in the refrigerator. This is great to make ahead for any occasion. Will melt in your mouth!