Coat 6-cup ring mold with nonstick cooking spray.
In medium saucepan, dissolve sugar and gelatin in 1 cup of the cold water. Stir over low heat until gelatin is completely dissolved. Pour into large bowl. Add remaining 2/3 cup water, the sparkling wine and orange juice. Chill in refrigerator until mixture mounds, about 30 minutes. Fold in sliced strawberries. Spoon into prepared mold.
Fan mango slices around bottom of mold in decorative fashion. Cover with plastic wrap. Refrigerate 2 hours or overnight.
To unmold, wrap warm towel over bottom of mold. Insert paring knife 1/4 inch deep around edge of mold. Very carefully pull gelatin from edge of mold, allowing air in between gelatin and mold. Unmold onto chilled serving plate. If gelatin does not release immediately, shake very gently.