2-4 lemons, depending on how juicy they are
Step by step
Wash the flowers thoroughly in a sieve.
Place in a deep jar - about 3 liters.
Pour the sugar over the flowers.
Squeeze the lemons - put the juice and peels in the jar. Pour enough water to cover all the ingredients well and leave the jar overnight, covered with a towel or gauze.
After this time, take some water from the jar into a bowl and mix with the yeast.
Transfer all the ingredients to a larger jar. I used a 5 liter water bottle. You could even cut its mouth, to make it wider.
Add the yeast dissolved in the water, mix everything well. Cover the bottle / jar with a gauze or towel and leave for 1-2 days until it infuses and acidifies. Taste periodically. Strain and place in the fridge when it seems fizzy enough. In a warm place, it can be ready even in one day.
Make sure you don't tighten the lid too much - it will definitely explode and this won't make your job very pleasant.
Keep in the fridge in bottles and serve cool with great pleasure :)