Bring a pot of water to a boil, then stir in the sugar until it dissolves.
Add the mulling spices, then allow the mixture to simmer for 10 minutes, stirring occasionally.
Take the sugar and spice mixture off the heat to let it cool, then strain out the solids and set the syrup aside.
Pour the pineapple rum into your serving pitcher, then add the apple cider and lemon juice on top of that.
Add in the bitters and 5 oz of the mulling spices syrup made earlier.
Add the apple slices and plenty of ice, stir, and serve!