Is refraining from drinking water while fasting, despite a medical warning that it would harm the kidneys, considered a sin, and is it permissible to fast in the upcoming Ramadan in this case?

Fasting Ramadan is obligatory for every capable, accountable Muslim. One who is harmed by fasting due to illness, or who requires treatment during the day, should break their fast and make up the missed days once they recover. If the illness is chronic and there is no hope of recovery, then one must feed a poor person for each day, as Allah Almighty says: (And whoever is ill or on a journey - then an equal number of other days. Allah intends for you ease and does not intend for you hardship) and as the Prophet (peace and blessings be upon him) said: (Indeed, Allah loves for His concessions to be availed of, just as He dislikes His disobedience to be committed). If a trustworthy doctor advises breaking the fast due to certain harm, then breaking the fast becomes obligatory, as Allah Almighty says: (And do not throw [yourselves] with your [own] hands into destruction) and as the Prophet (peace and blessings be upon him) said: (There should be neither harm nor reciprocal harm). It is advisable to consult another doctor if the harm is not clear.