Cook 1 1/2 cups large black tapioca in boiling water, 6 minutes; cover and let sit off the heat, 30 minutes. Bring 1 cup each water and sugar to a boil; transfer to a bowl. Drain the tapioca and soak in the sugar syrup. To serve, put 1/4 cup tapioca in a glass. Shake 1 cup cold green tea, 3 tablespoons soaking syrup, 1/4 cup milk and 1 tablespoon sugar with ice; pour over the tapioca.