Place the water and sugar into a saucepan and allow it to simmer until the sugar has dissolved. Zest and juice the oranges, lemon and limes then add the juice and half of the zest to the sugary water. Bring the mixture to the boil and turn off the heat to let it reduce.
Pour the mixture into a heatproof bowl to allow it to cool and then strain it into a pouring jug, removing the zest. Put the remaining fresh zest into your serving bottle and pour in the syrup. Serve when needed.