Lightly spray the insert of a 6-quart slow cooker with nonstick spray or line with a slow-cooker liner.

In a large bowl, whisk the eggs with the oil until combined. Add the cake mix and stir until moistened; the batter will be thick.

Fold in the fruit cocktail with juice, stirring gently to keep fruit intact. If using, fold in most of the coconut and reserve some for topping.

Pour the batter into the prepared slow cooker and spread evenly. Sprinkle remaining coconut on top if using.

Cover and cook on LOW for 2.5–3 hours, or until a toothpick inserted in the middle comes out clean.

For a slightly caramelized top, remove the insert (if safe) and place it under a broiler for 1–2 minutes, watching closely.

Let the cake rest in the slow cooker for 10–15 minutes before slicing. Serve warm with whipped cream, vanilla ice cream, or sweetened condensed milk.