Heat oven to 350 degrees F. Grease or spray bottom of 13x9-inch pan.

In large bowl, beat cake mix, pumpkin, water, oil, eggs and pumpkin pie spice with electric mixer on low speed until moistened, then on medium speed 2 minutes.

Pour into pan. Bake 25-35 minutes, or until toothpick inserted in center comes out clean.

Whisk together condensed milk and caramel sauce in a small bowl. Using a wooden skewer (or the handle of a wooden spoon), poke numerous holes in top of warm cake. Pour caramel mixture over cake and let it seep in until mixture has been absorbed, poking more holes as necessary. Let cake cool completely.

Gently fold cinnamon into whipped topping until just combined. Spread whipped topping over cooled cake and garnish with sprinkles. Refrigerate until ready to serve.