Combine prunes, raisins, currants, lemon juice, and 2 quarts water in a large Dutch oven; cover and let stand overnight.
Combine tapioca and remaining water; cover and let stand 1 hour. Drain well. Add drained tapioca and cinnamon to prune mixture. Cook over medium heat 30 minutes, stirring frequently. Add apricots, peaches, cherries, and orange and lemon slices; cook over low heat 30 minutes, stirring frequently. Remove from heat, and cool slightly. Remove cinnamon, and discard.
Spoon 1 teaspoon Cognac into each individual serving bowl; spoon soup into bowls, and serve immediately as an appetizer.
Note: Scandinavian Fruit Soup may be chilled and served as a dessert soup.