Grapefruit Soda

1 (12 fluid ounce) can frozen concentrated grapefruit juice, thawed

1 (12 fluid ounce) can frozen white grape juice concentrate, thawed

9 cups chilled club soda

Mix the grapefruit juice and white grape juice concentrates in a 1-quart pitcher until thoroughly combined. Store mixture in refrigerator. To serve, pour 1/3 cup of concentrate mix into a glass, and mix with 1 cup of cold club soda or sparkling water.