Beat the eggs in a mixing bowl with an electric mixer or in the bowl of a stand mixer. Add the box of cake mix, oil, and milk, and beat again at medium speed until light and fluffy.
Pour the cake batter into a 9x13 baking dish that has been sprayed with nonstick cooking spray and bake at 350 for 30-35 minutes until a toothpick inserted comes out clean.
Let the cake cool for 5-10 minutes, then use a fork or the end of a wooden spoon to poke holes in the cake. Try not to poke the holes too close together or so deep that they reach the bottom of the cake.
Drizzle the sweetened condensed milk over the top of the cake, making sure to get the milk into each of the poked holes. Repeat with the caramel sauce, reserving about ¼ of the jar to drizzle on top. Cool the cake completely.
While the cake cools, thaw out the Cool Whip. Once the cake has cooled to room temperature, spread the thawed Cool Whip evenly over the top of the cooled cake. Then drizzle the remaining caramel sauce and sprinkle the entire cake with the toffee bits. Refrigerate the cake for an hour before serving.