Add the apple juice, cinnamon sticks, cloves, and allspice berries to a medium saucepan. Place over medium heat and bring to a simmer.
Once simmering, remove from the heat and let sit for 30 minutes so the spices can steep into the juice.
To serve, reheat until warmed in the saucepan over medium-low heat. Portion 1 cup of spiced juice into a heat-proof mug, add 1/4 cup of spiced rum, and stir. Top with whipped cream and a sprinkle of ground cinnamon, if desired.
Notes
Nutritional information does not include garnishes.
Make a big batch ahead of time for parties. Add the spiced juice to a slow cooker and set to WARM to reheat. If you prefer, you can add the rum to the slow cooker as well... just be sure your guests know it's an "adults only" drink.