In a small bowl mix the butter with the sugar, vanilla, and pumpkin pie spice, until thoroughly combined.
Warm the pineapple juice in a medium saucepan until very hot, but not boiling. Remove from the heat and whisk in spiced butter until combined. Divide the rum among 4 mugs. Pour the pineapple juice into the mugs. Drop a cinnamon stick into each mug to use as a swizzle stick. Serve.