Place the sugar, water, orange juice and orange zest into a small saucepan and stir to combine.
Bring to a boil, then turn the heat down to low and gently simmer for 15-20 until it starts thickening and takes on a syrup consistency.
Set aside to cool, then store in the fridge until cold. I usually make this a day ahead to give the flavors a change to really develop.
Mix together all the fruit in a large bowl and pour the syrup over the top, tossing gently.
Garnish with fresh torn mint leaves and serve immediately.