1. In a large saucepan, cook sugar and water over low until sugar dissolves. Set aside to cool for 20 minutes. When cool, add ¼ cup mint and refrigerate for 6 hours.
2. Strain out and discard mint. Stir in both juices.
3. Divide among 4 ice-filled glasses. Fill each glass to top with seltzer. Garnish with mint sprigs.
Serves: 4. Per Serving: 140 calories, 37g carbs, 1g protein, 0g fat, 0mg sodium, 0mg cholesterol, 0g fiber