2 cups pitted fresh or frozen cherries, plus pitted frozen cherries, for serving
1 cup sugar
3/4 cup frozen limeade concentrate (half of a 12-ounce can)
1/2 cup fresh lime juice, plus lime wheels, for serving
Seltzer, for serving, optional
Combine the cherries, sugar and 1 cup water in a medium saucepan over high heat. Bring to a boil and reduce to a simmer. Carefully smash the cherries with a potato masher, then simmer the mixture until slightly reduced and dark red, about 10 minutes. Let cool for 10 minutes.
Strain the mixture through a strainer into a heatproof container, pressing on the cherry solids to extract all the juice. There should be about 1 3/4 cups of syrup. Let cool for 30 minutes.
Combine the cherry syrup with the limeade and lime juice in a pitcher and stir well. There will be about 3 cups total.
To serve: Either stir in 3 cups water if you want a still drink, or mix equal parts of the drink mix with seltzer in a glass. Serve over ice with frozen cherries and lime wheels.