I've made this cake for my sister's birthday every year for the last 30 or so years. 24 hours in the refrigerator makes it even better!
1 white or yellow cake mix (prepared according to package directions)
1/2 cup granulated sugar
1 cup milk
8 oz. whipped topping
12 oz. frozen coconut (thawed)
8 oz. sour cream
1/2 confectioner's sugar
Once cake layers are done, cool in pan for 10 minutes. While they are cooling heat milk and 1/2 cup granulated sugar over medium heat until hot. Turn layers out on waxed paper and spoon hot milk mixture over them. Mix last 4 ingredients and spread between layers as you stack them on cake plate. Frost top and sides as well. This will make 2 thick layers or 3 thinner layers. Refrigerate immediately!