Cut the cantaloupe in half. Remove the seeds and stringy fibers, scoop out the pulp with a large spoon and chop it coarsely/ Wash the strawberries and grapes under cold running water, picking out and discarding any fruits that are badly bruised. Remove and discard the stems.
Combine the cantaloupe, strawberries, grapes, apples, 1/2 cup of the lemon juice, the sugar and water in a 4 to 6 quart enameled or stainless steel saucepan. Bring to a boil over high heat, reduce the heat to low and simmer uncovered for 15 minutes.
Puree the soup through a food mill, or pour the entire contents of the pan into a large fine sieve set over a deep bowl and force the ingredients through with the back of a spoon, pressing down hard on the fruits before discarding any remaining pulp.
Stir the remaining 1/4 cup of lemon juice and the orange juice into the soup and refrigerate for at least 2 hours, or until thoroughly chilled.