HEAT oven to 350ºF.
DRAIN pineapple, reserving 1 cup juice. Prepare cake batter as directed on package, substituting reserved juice for 1 cup of the water. Pour into 15x10x1-inch pan sprayed with cooking spray.
BAKE 15 to 18 min. or until toothpick inserted in center comes out clean. Cool completely.
BEAT pudding mix and milk with whisk 2 min. Stir in pineapple; spread over cake. Cover with COOL WHIP; top with coconut and nuts. Keep refrigerated.