To make the syrup, bring the sugar and water to a boil in a small saucepan.
Once the sugar has dissolved, add the passion fruit, ginger and the lemon juice and zest and remove from the heat. Allow to cool.
To serve, pour a little of the syrup into a glass filled with ice then add some light rum and fill up with soda water. Add the mint and lemon and serve.
Alternatively, combine all the ingredients in a large jug.