01 - Preheat oven to 350°F. Generously 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 until smooth and well combined, about 2 minutes.
03 - Pour batter into prepared pan and spread evenly. Bake for 28-32 minutes until golden brown and a toothpick inserted in center comes out clean.
04 - Let cake cool in pan for 10 minutes. Using handle of wooden spoon, poke holes evenly across surface, spacing about 1 inch apart.
05 - Whisk together sweetened condensed milk and coconut milk in medium bowl until completely smooth.
06 - Slowly pour milk mixture evenly over warm cake, ensuring liquid seeps into all holes. Allow to absorb for 5 minutes.
07 - Whisk instant vanilla pudding mix, cold milk, and pineapple juice in separate bowl until thickened, about 2 minutes.
08 - Spread pudding evenly over surface of cake, filling holes completely.
09 - Cover pan tightly with plastic wrap. Refrigerate for at least 1 hour until completely cold and set.
10 - Spread thawed whipped topping evenly over chilled cake in smooth layer.
11 - Sprinkle toasted coconut generously over top. Garnish with fresh pineapple chunks and maraschino cherries if desired.
12 - Cut into 12 squares and serve cold. Store leftovers covered in refrigerator.