Prepare the Cake Base:
Preheat oven to 350°F (175°C).
Grease a 9x13 inch baking dish.
Prepare yellow cake mix according to package directions. Stir in crushed pineapple (with juice), coconut, and vanilla extract.
Pour batter into the prepared pan and bake for 30–35 minutes or until a toothpick comes out clean. Let it cool for 15 minutes.
Add Pineapple Filling:
While the cake is still slightly warm, use a fork or skewer to poke holes all over the surface.
In a bowl, mix sweetened condensed milk, drained crushed pineapple, and pineapple juice. Spoon this mixture evenly over the cake, letting it soak into the holes. Chill in the fridge for 1 hour.
Make the Fluffy Topping:
In a medium bowl, whisk together pudding mix and cold milk until thickened (about 2 minutes).
Fold in Cool Whip gently until smooth.
Spread evenly over the chilled cake.
Finish and Serve:
Sprinkle toasted coconut over the top for added texture and flavor.
Refrigerate for at least 1 hour before serving to let the layers set and flavors blend.