Prepare cake mix according to package directions, using the reserved pineapple juice and water for the liquid called for in the directions. Bake at 350° F. for about 35 minutes in a greased and floured 15 x 10 x 1 inch jelly roll (I used a 9-/12 x 13 pan). Cool in pan, set aside.
In a large bowl blend together cream cheese, pudding mix and milk until smooth. Fold in drained pineapple and spread over top of cake. Cover with whipped topping and sprinkle with nuts and coconut. Refrigerate.