Heat a medium saute pan over medium heat. Add cranberries, granulated sugar and water. Bring to a boil, then reduce heat and simmer for about 10 minutes, or until berries begin to burst. Remove from heat and pour cranberries into a bowl. Cover with plastic wrap and cool completely. Refrigerate until ready to use.
In a large mixing bowl, gently fold chilled cranberry sauce and non-dairy whipped topping together (the cranberry sauce will be fairly solid; gently press with your spatula to break up). Fold in mandarin oranges, pineapple and mini marshmallows until coated.
Pour into a serving dish and chill until ready to serve
If desired, top with sugared cranberries. Simply roll some cranberries in granulated sugar and carefully place on top of the cranberry fluff salad.