For chocolate sauce, in a 1-1/2-quart saucepan, combine apple juice and/or grape juice concentrate, and cocoa powder. Add honey.
Cook and stir over medium heat until bubbly. Whisk in water and vanilla or liqueur. Remove from heat. Pour into a container. Cover and chill in the refrigerator 8 hours or overnight.
For each sundae, scoop about 1/2 cup frozen yogurt into a dish. Top with fruit. Drizzle with chocolate sauce. Garnish with a mint sprig. Makes about 1-1/2 cups sauce (24 servings).