Mix sugar and water in a small saucepan and bring to the boil. Let it boil down like a syrup for about 10 minutes. Allow to cool slightly. Wash and clean the strawberries and cut into pieces. Add orange juice and sugar syrup and puree. Pour into a metal bowl and place in the freezer for at least 4 hours, stirring occasionally.
Take out the sorbet 10 minutes before serving, let it thaw and beat with a hand blender until smooth. Fill into 4 glasses (if desired with a piping bag) and pour 1 tablespoon of Campari over each. Top up with sparkling wine or prosecco.