All praise is due to Allah, and may peace and blessings be upon the Messenger of Allah.
The Prophetic Sunnah mentions that the person who caused the evil eye washing himself is among the means used to treat someone afflicted by the evil eye. However, there is no established evidence from the Prophet ﷺ indicating that using ablution water for protection against the evil eye before it occurs is prescribed in Islam.
Therefore, it is not prescribed to perform ablution collectively in one shared container and use the water as a means of protection against the evil eye when no one has actually been afflicted. This practice has no supporting evidence in Islamic law and may lead to indulging in doubts and obsessive thoughts.
The prescribed protection against the evil eye is achieved by regularly observing the authentic remembrances and supplications reported from the Prophet ﷺ, while placing one's trust in Allah and maintaining good expectations of Him.
In conclusion, using ablution water for protection against the evil eye before it occurs is not prescribed. Rather, protection should be sought through the Islamic remembrances established in the Sunnah.
And Allah knows best.