Preparation Stir 1 tablespoon sugar and 1/8 teaspoon salt into juice until dissolved. Stir in soju and add sugar to taste. Pour over ice in tall 8- to 10-ounce glasses (about 1/2 cup grapefruit mixture per glass) and top with a splash of club soda. Cooks' note:Grapefruit mixture, without soju, can be made 4 hours ahead and chilled. Add soju to mixture just before serving.
Preparation Stir 1 tablespoon sugar and 1/8 teaspoon salt into juice until dissolved. Stir in soju and add sugar to taste. Pour over ice in tall 8- to 10-ounce glasses (about 1/2 cup grapefruit mixture per glass) and top with a splash of club soda. Cooks' note:Grapefruit mixture, without soju, can be made 4 hours ahead and chilled. Add soju to mixture just before serving.