Prepare the berries: Add blueberries, raspberries, and lemon slices to a large pitcher. Lightly press some of the berries to release their juices while keeping some whole for texture.

Add iced tea: Pour chilled blueberry iced tea into the pitcher and stir gently to combine with the fruit.

Add sparkle and serve: Top with sparkling water just before serving. Add ice cubes, stir lightly, and garnish with fresh berries or mint if desired.