01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan thoroughly with cooking spray or butter.
02 - Combine yellow cake mix, eggs, crushed pineapple with juice, vegetable oil, and water in a large mixing bowl. Beat with electric mixer on medium speed for 2 minutes until smooth and well blended.
03 - Pour batter into prepared pan, spreading evenly. Bake for 28-32 minutes until golden brown and a wooden toothpick inserted in center comes out clean.
04 - Allow cake to cool in pan for 10 minutes. Using the round handle of a wooden spoon, poke holes evenly across entire cake surface, spacing about 1 inch apart.
05 - Whisk together sweetened condensed milk and coconut milk in medium bowl until completely smooth and combined.
06 - Slowly pour milk mixture evenly over warm cake, ensuring liquid fills the poke holes. Allow cake to absorb mixture for 5 minutes.
07 - Whisk instant vanilla pudding mix, cold milk, and pineapple juice in separate bowl for 2 minutes until thickened. Spread pudding evenly over cake surface.
08 - Cover pan with plastic wrap or foil. Refrigerate for minimum 1 hour until completely chilled and set.
09 - Spread thawed whipped topping evenly over entire surface of chilled cake.
10 - Sprinkle toasted coconut generously over whipped topping. Garnish with fresh pineapple chunks and maraschino cherries if desired. Cut into squares and serve cold.