Just the contents of the cake mix can of crushed pineapple in its own juice. (No need to use a mixer, just stir it with a spoon. No need to follow the directions on the box), & combine it with the crushed pineapple.
The mixture starts to froth. Once it's all mixed up,grease and simply pour it into a 9 x 13 cake pan & bake 350 for 30 minutes. No need to ice the cake unless you want to do it.