01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan 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 smooth.
03 - Pour batter into prepared pan. Bake for 28-32 minutes until golden brown and a toothpick inserted in the center comes out clean.
04 - Let cake cool in pan for 10 minutes. Using the handle of a wooden spoon, poke holes evenly across the entire cake surface, spacing about 1 inch apart.
05 - Whisk sweetened condensed milk and coconut milk together until smooth. Slowly pour over warm cake, ensuring the liquid seeps into the holes.
06 - Whisk instant vanilla pudding mix, cold milk, and pineapple juice in a medium bowl for 2 minutes until thickened. Spread evenly over the cake.
07 - Cover pan with plastic wrap and refrigerate for at least 1 hour until completely set and chilled.
08 - Spread thawed whipped topping evenly over the chilled cake surface using an offset spatula.
09 - Sprinkle toasted coconut over the top. Decorate with fresh pineapple chunks and maraschino cherries if desired. Slice into 12 squares and serve cold.