Bring the sugar, orange juice, lemon juice and coconut milk to a boil. Simmer for 1-2 minutes, stirring until the sugar has completely dissolved. Remove from the heat and cool.
Peel the mango, cut the flesh from the core and puree in a blender with the coconut syrup. Finish the sorbet in an ice cream maker or pour into a shallow metal bowl, cover and freeze at least 4 hours, stirring frequently with a fork.
To serve, scoop the sorbet into ice cream cones.