Gewürztraminer Grape Juice Spritzer

From the story about Sarah Henry’s Farmsteads of the California Coast

18 seedless red grapes or red raspberries, frozen
1 bottle Gewürztraminer Grape Juice, chilled
1 liter bottle seltzer water, chilled

Divide the fruit between 6 champagne flutes. Fill the flutes half full of gewürztraminer grape juice and top with seltzer water. Stir and serve.