Bake: Preheat oven to 350°F. Line a 9x13 pan with foil and grease with cooking spray. Mix the cake mix, eggs, water, and oil on high for 2 minutes. Pour into the pan and bake for 23–25 minutes (until a toothpick comes out clean).
Poke: While the cake is still warm, use the blunt end of a wooden spoon to poke approximately 75 holes evenly across the surface, going nearly to the bottom of the cake.
Drench: Whisk together the butterscotch syrup and sweetened condensed milk. Pour slowly and evenly over the cake. Use a spatula to sweep the mixture into the holes.
Chill: Cover and refrigerate for at least 2 hours (or up to 2 days) until completely chilled.
Finish: Just before serving, spread the whipped topping over the cake and sprinkle generously with toffee bits.