Wash cranberries, removing stems and soft berries. Cook according to package instructions until berries are soft. If using sugar instead of sugar substitute, add sugar while cranberries are cooking. Chop berries in blender or put through food mill. Add 2 cups water. Strain through cheesecloth or several thicknesses of nylon net. Add orange juice concentrate and sugar substitute (if using). Dilute with enough water to make 8 cups.