Bring first 3 ingredients to a boil in a saucepan, and cook, stirring constantly, 4 to 5 minutes or until sugar mixture reaches a syrup consistency. Discard mint leaves, and cool sugar syrup completely.
Combine pineapple, banana, apple, grapes, and strawberries in a large bowl. Pour syrup over fruit mixture; toss gently. Cover and chill at least 1 hour. Serve with Sour Cream Sauce.