Preheat the oven to 350ºF and lightly grease an 8 X 8" square baking dish, or a 7 X 6.5" rectangular dish.
Add the fruit cocktail (including the juices) to a medium-sized mixing bowl, along with the sugar and self-rising flour.
Stir everything together until well combined.
Pour the mixture into the prepared baking dish and bake in the oven for 25-35 minutes (using an 8X8" dish will take less time than using a 7.5X6 dish). The cake is done when it is "golden and bubbly" and a toothpick comes out clean when inserted into the center.
Remove from the oven and allow to cool for 5 minutes.
Serve with ice cream, a dollop of whipped cream, or frosting.
Notes
Self-rising flour: If you don't have self-rising flour on hand, you can make your own by combining 1 cup of flour, 1 ½ teaspoons of baking powder, and ¼ teaspoon salt. Sift for the best results.