Makes about 7 cups
1 (12-ounce) can frozen lemonade concentrate, thawed and undiluted
1 (10-ounce) package frozen strawberries, partially thawed, for frozen raspberries
3 tablespoons sugar
1 (1-liter) bottle club soda, chilled
Process first 3 ingredients in a blender until smooth, stopping to scrape down sides.
Pour strawberry mixture through a wire-mesh strainer into a large pitcher, discarding seeds; stir in club soda. Serve over ice.