Puree berries, peaches or mangoes to make vibrant "syrups" for swirling with ice cream and sparkling water. (Or skip the ice cream to make refreshing fresh-fruit sodas.)
For syrup: In a blender or food processor, combine desired fruit, sugar and lemon juice. Blend or process until smooth. Strain through a fine-mesh sieve. Chill syrup, covered, for 4 hours or up to 3 days.
For each soda: Add 1/4 cup of the chilled fruit syrup and half a scoop of ice cream to a tall glass. Blend with spoon. Fill glass three-quarters full with carbonated beverage. Add two scoops ice cream. Serve immediately.