4 cups water
1 cup quick cooking pearl tapioca
6 cups brewed black tea
1/4 cup sweetened condensed milk
4 teaspoons white sugar, or to taste
Bring water to a boil in a pot, add tapioca pearls, and cover pot. Reduce heat to medium-low and simmer for 5 minutes. Drain pearls and set aside.
Pour brewed tea, condensed milk, and sugar into a pitcher; stir to dissolve sugar. Refrigerate tea mixture until chilled, about 1 hour.
Scoop tapioca pearls into 4 large glasses, about 2 tablespoons each. Fill each glass with tea mixture; top with ice.