You must sterilise your jars before you start and you will need to check your ferment every day for four to five days.

Juice the lemons and pour the juice through a sieve. Combine the lemon juice, ginger, whey and sugar in a 3-litre sterilised jar and top up with mineral water, leaving 2.5cm at the top of the jar. Give it a good shake and leave it at room temperature for two days, releasing gas as you need to by releasing then refastening the lid.

After this time, decant it into glass bottles, adding a little of the 1/2 tbsp sugar to each. Seal and ferment for a further two to three days (burping every day) until you see bubbles. Put in the fridge to stop any further fermentation. Will keep in the fridge for a week.