1/2 cup freshly squeezed lime juice, from about 4 limes, plus lime wedges, for garnish
1/2 cup mezcal
1/2 teaspoon ground cinnamon
Combine the cinnamon stick, vanilla bean, 1 cup of the sugar and 1 cup water in a small saucepan. Place over medium-high heat and bring to a boil. Reduce to a simmer and cook until the sugar is dissolved, 5 to 8 minutes. Turn off the heat and allow to cool to room temperature, about 10 minutes.
Pour the cooled syrup into a pitcher. Add the horchata, lime juice and mezcal. Stir to combine.
In a small, shallow dish, combine the remaining 1/4 cup sugar and the ground cinnamon. Dip the rims of cocktail glasses into the horchata cocktail mixture, then into the cinnamon sugar. Add ice to the sugar-rimmed glasses. Add the horchata cocktail and garnish with lime wedges. Drink up!