Preheat and Prepare:
Preheat your oven to 350°F (175°C). Line a 9×13-inch baking dish with parchment paper or spray with non-stick cooking spray.

Mix the Cake Batter:
In a large mixing bowl or stand mixer, combine the cake mix, pudding mix, sour cream, oil, eggs, vanilla, and warm water. Beat on medium speed for about two minutes, scraping down the sides as needed, until smooth.

Bake the Cake:
Pour the batter into the prepared pan and spread it evenly. Bake for 30–35 minutes, or until the cake springs back when gently touched and a toothpick comes out clean.

Make the Caramel Mixture:
While the cake bakes, whisk together the sweetened condensed milk, ¾ cup of caramel sauce, and a pinch of flaky sea salt until well combined.

Poke the Cake:
When the cake is fresh out of the oven, use the handle of a wooden spoon or a smoothie straw to poke holes evenly across the surface, about an inch apart.

Add the Caramel Soak:
Pour the caramel mixture slowly over the cake, making sure it fills the holes and spreads evenly across the top.

Cool and Chill:
Let the cake cool to room temperature, then cover and refrigerate for at least 4 hours. Chilling allows the caramel mixture to absorb completely, making the cake more flavorful and easier to slice neatly.

Top the Cake:
Once chilled, evenly layer the thawed whipped topping across the surface. Sprinkle on the toffee bits and drizzle with the remaining ¼ cup of caramel sauce.

Serve:
Slice into squares and serve cold for the best texture and taste.