Prepare the cake: Mix and bake the banana cake in a greased 9x13 baking dish according to the package directions. Let it cool completely.

Use the end of a wooden spoon or straw to poke holes all over the cooled cake, about 1 inch apart.

Add the strawberry jam: Microwave the jam for 1–2 minutes until it's pourable. Carefully pour it over the cake, making sure it seeps into the holes.

In a bowl, whisk the pudding mix with cold milk for 2 minutes. Let it set for 5 minutes, then stir in the well-drained crushed pineapple.

Evenly distribute the pudding mixture over the cake. Cover and refrigerate for at least 1 hour, or overnight if you're making it ahead.

Spread the Cool Whip over the pudding layer. Drizzle with chocolate syrup, add colorful sprinkles, and place maraschino cherries on top.

Slice into squares and dig in!