Stir together apple cider and 4 tablespoons caramel ice cream topping in a 4-quart slow cooker until smooth. Cover and cook on Low for 3 to 4 hours, or on High for 1 1/2 to 2 hours.
Mix together sugar, salt, and apple pie spice in a small shallow bowl. Pour remaining 2 tablespoons caramel topping into a small saucer.
Dip the rims of 8 mugs or heatproof glasses into caramel topping, evenly coating the rim; then dip into spice mixture. Ladle hot cider into mugs. Add 3 tablespoons spiced rum to each mug and garnish with a cinnamon stick.