Peel the lemons thinly with the potato peeler. There must be no white skin on it. Mix the lemon zest, citric acid and sugar. Boil 1 liter of water and pour over it. Let the mixture cool down. Halve the lemons and squeeze the juice and add to the mixture. Let the drink stand for a day and strain it. Pour the lemon drink into bottles and seal. Store in the refrigerator.
You can drink the drink neat or mixed with mineral water.