Preheat oven to 350°F (175°C) and grease a 9x13-inch baking dish.
Prepare the cake mix according to the package instructions, replacing the water with the pineapple and its juice.
Fold in shredded coconut and bake as directed.
Once baked, poke holes all over the cake with the handle of a wooden spoon.
Pour the sweetened condensed milk over the cake, allowing it to seep into the holes.
In a bowl, beat cream cheese until smooth, then mix in powdered sugar and vanilla extract.
Fold in whipped topping and spread evenly over the cooled cake.
Sprinkle with extra shredded coconut, refrigerate for at least 2 hours before serving.