Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch baking pan.
In a large bowl, combine cake mix, water, oil, and eggs. Beat until smooth.
Pour batter into prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
While cake is baking, make the caramel sauce. In a medium saucepan, combine sweetened condensed milk, hot fudge topping, and caramel topping. Heat over medium heat, stirring constantly, until sauce is smooth and bubbly.
Pour caramel sauce over hot cake.
Let cake cool completely before frosting.
To frost the cake, spread whipped topping over the top and sides of the cake.
Sprinkle with chopped Butterfinger candy bars.