Wash lemons and cut into slices. Wash the umbels and put them in a stone pot and pour 10 liters of water with the vinegar, sugar and lemon wedges over them. Cover the pot with a cloth and place in a warm, sunny place. Stir the liquid every now and then.
Fermentation begins after 2 to 4 days. Then pour the liquid through a cloth and fill it into bottles. (Bottles with swing top are best.) Store in a cool place.