Preheat oven to 350 degrees. Prepare three 8 or 9 inch round cake pans with butter and sugar.
In a mixing bowl, combine the cake mix, pudding mix, oil, 7-Up (and juice) and 4 eggs. Beat on medium speed until well blended, about 2-3 minutes. Divide evenly into the three pans.
Bake for 30 minutes until toothpick inserted in center comes out clean. Cool in the pans for 5 minutes, invert and let cool completely.
In a medium sauce pan, combine sugar, butter, pineapple and the beaten eggs. Cook over low to medium low heat, stirring constantly. Increase heat to medium and cook until thick and bubbly. Remove from heat and stir in the bag of coconut.
Spread the warm icing over the cake layers and enjoy!