Boil the water and allow to cool. Add 3 glasses of apple cider vinegar and sugar, mixing well so that the sugar dissolves. Add the well-cleaned elderberry flowers and the sliced lemons.
Leave to rest in the sun for 3 days, stirring occasionally.
At the end, squeeze and filter everything (with the help of a colander or fine gauze), mix and cook the juice in a pan. Boil for a few minutes before bottling hot.
