Pour 8 cups boiling water into a slow cooker. Add 16 chai tea bags; secure the lid with the tea bag tabs hanging outside and steep 10 minutes. Remove the tea bags. Stir in 1/2 cup each spiced rum and vanilla-flavored vodka and 2 cinnamon sticks. Cover and cook on low for 2 hours. Stir in 2 cups sweetened condensed milk; switch to the warm setting until ready to serve. Ladle into mugs and garnish with cinnamon sticks.
If you don't have a slow cooker, keep these drinks warm in a saucepan on the stovetop over low heat.
Photograph by Johnny Miller