Preheat oven to 425°F. Spray a muffin pan with baking spray or line with parchment or paper liners.
In a large bowl, combine the muffin mix, chopped apple, shredded carrot, walnuts, and coconut.
1 13.9-ounce Betty Crocker Cinnamon Streusel Muffin Mix, ½ cup chopped apple, ½ cup shredded fresh carrot, ½ cup chopped walnuts, ½ cup flaked coconut
In a separate bowl, whisk together the vegetable oil, eggs, and undrained crushed pineapple.
¼ cup vegetable oil, 2 large eggs, 1 8-ounce can crushed pineapple in juice, undrained
Add the wet ingredients to the dry ingredients and stir just until combined.
Divide the muffin batter evenly among the muffin cups, filling each about ¾ full. Sprinkle the streusel topping over the muffins and press lightly so it sticks.
Bake for 15–20 minutes, or until the tops are golden brown and a toothpick inserted into the center comes out clean.
Cool in the pan for 15 minutes before transferring to a wire rack.
In a small bowl, whisk together the powdered sugar and water until smooth and drizzleable. Drizzle over the warm muffins before serving.
½ cup powdered sugar, 1 –2 teaspoons water