Add the rosé wine and St. Germaine to a large pitcher and stir. Add the strawberries, blueberries, and basil and chill for at least 1 hour. Can be made 3 hours ahead. Cover; keep chilled.

Pour sparkling water or prosecco over wine mixture. Stir to blend. Ladle sangria into ice filled glasses, top with berries and basil leaves and serve right immediately. Enjoy!