Heat oven to 400*. Grease bottom only of 13x9-inch pan with shortening or cooking spray.In large bowl,stir together both muffin mixes,apple,carrot,walnuts and coconut.In medium bowl,stir together oil,eggs and pineapple;stir into muffin mixture.Spread in pan.Sprinkle with streusel (from muffin mixes).
Bake 43 to 45 minutesor until toothpick inserted in center comes out clean.Cool 15 minutes.
In small bowl,mix powdered sugar and enough of the 2 to 4 teaspoons of water until smooth and thin enough to drizzle. Drizzle over warm cake.