Preheat oven to 350ºF. Spray a 9x13" pan with cooking spray and set aside.
In a mixing bowl, combine the dry angel food cake mix with the crushed pineapple, juice and all. Stir well.
Pour cake batter into prepared pan and bake in preheated oven for 35-40 mins. Keep checking the cake after about 30 minutes. The cake will be springy to the touch when cooked through and golden brown on the top.
Let cool and then cut into squares. Serve with whipped topping and fruit. Enjoy!