Place the pitted cherries in a large mixing bowl. Add the sugar or agave, lime juice and salt. Stir until the cherries are evenly coated. Set aside at room temperature for 1 hour to macerate the cherries.

Drain the cherry mixture, collecting and reserving all the juice. Thread the macerated cherries amongst 8 cocktail skewers and set aside for garnish.

Stir together the reserved cherry juice and seltzer in a small pitcher.

Fill 8 highball glasses with ice cubes. Pour the cherry sparkler over the ice and garnish each glass with a skewer of cherries and a sprig of mint. Serve immediately.