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 bowl. Beat with electric mixer on medium speed for 2 minutes until batter is smooth and well combined.
03 - Pour batter into prepared baking pan. Bake for 28-32 minutes until golden brown and a toothpick inserted in center comes out clean. Remove from oven and let cool for 10 minutes.
04 - Using the handle of a wooden spoon, poke holes evenly across the entire surface of the warm cake, spacing about 1 inch apart. Press holes about three-quarters of the way through the cake.
05 - Whisk together sweetened condensed milk and coconut milk in a medium bowl until completely smooth and combined.
06 - Slowly pour the milk mixture evenly over the warm cake, concentrating on getting it into the poke holes. Let stand for 15 minutes to allow absorption.
07 - Whisk instant vanilla pudding mix, cold milk, and pineapple juice in a separate bowl for about 2 minutes until mixture begins to thicken. Spread evenly over the cake.
08 - Cover pan with plastic wrap or foil. Refrigerate for at least 1 hour until completely cold and set, preferably 2-3 hours for best results.
09 - Spread thawed whipped topping evenly over the chilled cake surface using an offset spatula or butter knife.
10 - Sprinkle toasted coconut generously over the top. Decorate with fresh pineapple chunks and maraschino cherries if desired. Slice into 12 squares and serve cold.