Preheat oven to 350. Lightly grease a 13 x 9 inch baking pan.
Place cake mix, water, oil, and eggs in mixing bowl. Blend with mixer on low speed for 1 minute. Stop machine and scrape down sides of bowl. Increase mixer speed to medium and beat 2 minutes more, scraping sides down again if needed. The batter should look thick and well blended. Pour batter into prepared pan. Place pan in oven.
Bake cake until it springs back when lightly pressed with your finger, 35-38 minutes. Remove pan from oven and place on wire rack. Immediately poke holes in top of cake with drinking straw or chopstick.
Prepare topping. Place caramel topping and sweetened condensed milk in bowl and stir to combine. Spoon mixture over warm cake so that it can seep down into the holes. Measure out half of the crushed candy bars and sprinkle the pieces over the cake.
Place whipped topping and cream cheese in mixing bowl and blend with mixer on low speed until smooth and combined, 1 minute. Spread the mixture over the top of the candy. Sprinkle remaining candy pieces on top. Place pan, uncovered, in refrigerator to chill the cake for about 20 minutes before cutting it into squares and serving.