Measure the sugar into a food processor. Add the mint and pulse until the mint is finely chopped. Scrape the sugar into a large bowl and add the lime juice and sparkling water, stirring until the sugar is dissolved.
Divide the frozen fruit pieces among 20 ice pop molds, then fill with the lime mixture, leaving about 1/4-inch head space for expansion. Secure the lids, insert the sticks through the holes, making sure that they’re straight and that 1 1/2 to 2 inches remains exposed (for easy grasping). Slide the molds into the freezer.
When the ice pops are firmly set—this will take a couple of hours in most freezers—they’re ready to serve. Remove the lids from the molds, then either squeeze the sides of each mold to free the pop or run the mold under warm water to release the pops.