Combine the cider, cranberry juice, gelatin and sugar in a saucepan and allow the gelatin to bloom at room temperature for about 5 minutes.
Heat the mixture over low heat, stirring occasionally until the gelatin and sugar are completely dissolved. Remove from heat and allow it to cool slightly.
Stir in cinnamon whiskey. Spray a 9 x 9-inch glass baking pan with cooking spray and pour in mixture.
Set the pan in the fridge, uncovered, for about 2 hours or until gel is set.
To remove from the baking pan, run a warm paring knife around the perimeter of the pan and turn the pan upside down onto a cutting board with slight force to release the gelatin. Slice the square into 8 x 8 portions and separate them onto a platter. Dust the tops with cinnamon sugar and garnish with fresh slices of cranberries.