Put sugar and 1 cup water into a medium saucepan; bring to a simmer over medium heat, stirring to dissolve sugar. Remove from heat; let cool slightly.
Puree fruit, syrup, lemon juice, and salt in a blender. Pour through a fine sieve into a bowl. Refrigerate until cold, at least 30 minutes (up to 2 days).
To serve, fill 8 medium glasses with ice; pour 1/2 cup puree into each glass, and top off with sparkling water. Stir to combine. Serve immediately.