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 until smooth, about 2 minutes.
03 - Pour batter into prepared pan. Bake for 28-32 minutes until a toothpick inserted in center comes out clean.
04 - Let cake cool for 10 minutes. Using handle of wooden spoon, poke holes all over cake at 1-inch intervals, pressing halfway through.
05 - Whisk sweetened condensed milk and coconut milk in medium bowl until completely blended. Pour slowly over warm cake, ensuring liquid fills holes.
06 - Whisk instant vanilla pudding mix, cold milk, and pineapple juice in separate bowl until thickened, about 2 minutes. Spread evenly over cake.
07 - Cover pan with plastic wrap or foil. Refrigerate for at least 1 hour until completely cold and set.
08 - Spread thawed whipped topping evenly over chilled cake using offset spatula.
09 - Sprinkle toasted coconut over top of cake. Garnish with fresh pineapple chunks and maraschino cherries if desired.
10 - Cut into 12 squares and serve cold. Store leftovers refrigerated.