Rub the lemon zest into the sugar with your fingertips before adding water for an even stronger lemon flavour. | If your lemons are very sharp, add an extra tablespoon of honey. | Replace half the cold water with sparkling water for a fizzy version. | Add strawberries, raspberries, or fresh basil for easy flavour variations. | Keeps well in the fridge for 2-3 days. Freeze leftovers into ice lollies or ice cubes for drinks later in the week.