I'm not being naive, I understand where you are coming from, but, I wouldn't say that the money is a need in order to live (fairly narrow definition).
it is one of a means to get clean water, if I don't have the coins - do I have to die?
I have options: I could try
(outside of industrially polluted areas) boiling rain water and distilling the steam,
stealing the water bottles,
begging for water,
bartering services or goods for water,
moving to a less polluted area,
getting a job in the water bottling plant and being paid in kind,
get given water by wealthier friends/family/government/aid
The government of the country or other countries could get off their behinds and build a free clean water delivery system for all human beings
having money and buying the water in bottles may be a more practical, legal, easy or less degrading option than any or all of these, and I believe everyone has a right to clean water full stop (and in fact I think it should be free to all, given that it is a need to the most narrow definition of life).
but unless this is a hypothetical alternate reality (which is where my post came from) where there is (by some obscure law of physics) absolutely no alternative but to exchange coins for water, the coins are not a need. The water is a need and a means of access to it is implied in that need, because its useless if you can't drink it, but the way of getting access is not a need.
by contrast, if you asked if the coins were a need in order to thrive, with self-respect, legally, in Sri Lanka in areas where the natural water supply is poisonous, within the current system as it is now (iI have to bow to your knowledge of the system in Sri Lanka, as I have none), without the aid of bartering or being paid in kind, and accepting no offers of help to get water*, then yes, but I think you have to qualify it thus.
* none of which I think people should have to do to get water