Preheat oven to 350°F (175°C). Grease a 9x13-inch baking pan.
In a large bowl, mix cake mix, eggs, oil, and water until smooth, about 2 minutes.
Fold in 3/4 cup Heath toffee bits.
Pour batter into the prepared pan and bake for 25–30 minutes, until a toothpick comes out clean.
Let cake cool in the pan for 10 minutes, then transfer to a wire rack or leave in pan.
Spread chocolate frosting over cooled cake.
Drizzle caramel sauce on top and sprinkle with remaining 1/4 cup toffee bits. Add a pinch of sea salt, if using.
Serve with a dollop of whipped cream, if desired.