Heat 1 cup fruit juice in small saucepan until it just simmers, do not cook for any length of time. Turn off heat and stir in sugar, if using. Place remaining 1 cup cold juice in a medium bowl and sprinkle gelatin over, stir, let sit for 2 minutes and stir again. Add warm juice to cold juice, stir, and pour mixture into 8 by 8-inch pan. Refrigerate until firm, 4 hours, and cut into cubes.
c.1997, M.S. Milliken & S. Feniger, all rights reserved