To a 9 x 13 pan, add both cans of crushed pineapple with the juice.
Spread dry cake mix over the top.
Drizzle sweetened condensed milk over the dry cake mix.
Pour the melted butter as evenly as possible across the top.
Sprinkle the coconut on the top.
Bake at 350 degrees for 45-50 minutes until golden brown.
Notes
You may think that you can skip the butter when you are using the condensed milk. But don't skip it! The butter and yellow cake is too good together. That is where all the goodness from a dump cake comes from. Otherwise, it's just fruit.
Have you ever made a dump cake in a crock pot? I made this Crock Pot Apple Cherry Dump Cake recently and it was just as good as in the oven. I'm sure you could make this recipe in the crock pot too.