Watermelon candies are an odd duck. A slice of watermelon is sweet enough to almost taste like a candy already, and you can turn watermelon rinds into a summer candy by simmering them with syrup.

Target's candy section is about to get a little sharper. Retro Sours are back with four new flavors—Watermelon, Passionfruit, Raspberry, and Mango—but there's one important detail to note: you'll only ...