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 until smooth, about 2 minutes.
03 - Pour batter into prepared pan. 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 all over surface at 1-inch intervals, pressing about three-quarters through cake.
05 - Whisk sweetened condensed milk and coconut milk in medium bowl until fully combined. Slowly pour evenly over warm cake, allowing mixture to seep into holes.
06 - Whisk instant vanilla pudding mix, cold milk, and pineapple juice in separate bowl until thickened, about 2 minutes. Spread pudding evenly over cake surface.
07 - Cover pan with plastic wrap and refrigerate for at least 1 hour or until completely chilled, ideally 2-3 hours for best results.
08 - Spread thawed whipped topping evenly over chilled cake using offset spatula or back of spoon.
09 - Sprinkle toasted coconut over top. Garnish with fresh pineapple chunks and maraschino cherries if desired.
10 - Cut into 12 squares and serve cold. Cake can be stored covered in refrigerator for up to 3 days.