Without spending a single penny more, I submerge the apples in boiling water. My granny acted in like manner!

Five green apples
One water liter
50 grams of caster sugar
One liter of boiling or filtered water
Boil a liter container in a saucepan of water for 30 minutes to sterilize it.

Allow it to dry naturally.

Bring one liter of running water to a boil in a saucepan. Put the sugar in two glasses and stir. Allow it to cool fully.

After washing, thoroughly dry, and crate the apples into pieces.

After placing them in the container, add the boiling water and syrup and stir well. Make sure the fruit is well immersed in the liquid. Use sterile gauze to seal and fasten with an elastic band. Place a towel over it and keep it somewhere dry, cold, and dark.

Give the apples a three-week rest, examining often to ensure sure mold hasn't taken hold of them. After the 21 days, drain the liquid (it will smell pleasant) and put it back in the jar. Once again, leave it in the dark for 28 days, stirring it every other day.

The apple cider vinegar may then be used as desired at this point.