Bake the chocolate cake according to the package instructions in a 9x13-inch pan.
Remove the cake from the oven and, while still warm, poke holes all over the top using the handle of a wooden spoon.
Pour the sweetened condensed milk evenly over the cake, letting it soak into the holes.
Drizzle the caramel sauce over the top as well.
Allow the cake to cool completely, then spread the whipped topping over the cake.
Sprinkle the crushed candy bars on top before serving. Store in the refrigerator.