In a medium bowl, toss the chopped apples with ground cinnamon until evenly coated. This step infuses every apple piece with warm spice.

In a separate bowl, whisk together the instant vanilla pudding mix and cold milk until the mixture thickens. This usually takes about two minutes. Let it sit for a minute to fully set.

Gently fold two thirds of the thawed whipped topping into the pudding mixture. Reserve the remaining whipped topping for the top of the cake. Fold carefully to keep the mixture light and airy.

Spread a thin layer of caramel sauce over the bottom of a 9x13 inch baking dish. This thin base layer helps prevent sticking and adds a little extra caramel flavor to the first bite.

Arrange a single layer of graham crackers over the caramel sauce. Break a few crackers as needed to cover the surface evenly.

Spread half of the pudding mixture over the graham crackers. Use a spatula or the back of a spoon to create an even layer.

Sprinkle half of the cinnamon-coated apples evenly over the pudding layer. Try to distribute the apples so each slice gets a good amount.

Drizzle half of the remaining caramel sauce over the apples. A squeeze bottle makes this step neater, but a spoon works just fine.

Repeat the layers: graham crackers, the remaining pudding mixture, the remaining apples, and the remaining caramel sauce.

Finish with a final layer of graham crackers on top. Press down very lightly so the layers hold together without squishing the filling.

Cover the dish with plastic wrap or a lid and refrigerate for at least four hours, or overnight. The graham crackers need time to soften and absorb moisture from the pudding and caramel.

Before serving, spread the reserved whipped topping over the top layer. Drizzle with extra caramel sauce if desired. Slice into squares and serve cold.