I am aware of a hadith where Prophet Muhammad (PBUH) instructed a person to give his bath water (water he used to wash his body) to another person (I don't know if he was a Sahabi) because it was believed that he gave the other person the evil eye.
Imam Ahmad, Malik, al-Nasai and Ibn Hibban narrated from Sahl ibn Hanif that the Prophet (peace and blessings of Allah be upon him) came out and traveled with him towards Makkah, until they were in the mountain pass of al-Kharar in al-Jahfah. There Sahl ibn Hanif did ghusl (bathed), and he was a handsome white-skinned man with beautiful skin. ‘Amir ibn Rabi'ah, one of Banu ‘Adiyy ibn Ka'b looked at him whilst he was doing ghusl and said: “I have never seen such beautiful skin as this, not even the skin of a virgin,” and Sahl fell to the ground. They went to the Messenger of Allah (peace and blessings of Allah be upon him) and said, “O Messenger of Allah, can you do anything for Sahl, because by Allah he cannot raise his head.” He said, “Do you accuse anyone with regard to him?” They said, “‘Amir ibn Rabi'ah looked at him.” So the Messenger of Allah (peace and blessings of Allah be upon him) called ‘Amir and rebuked him strongly. He said, “Why would one of you kill his brother? If you see something that you like, then pray for blessing for him.” Then he said to him, “Wash yourself for him.” So he washed his face, hands, forearms, knees and the sides of his feet, and inside his izar (lower garment) in the vessel. Then that water was poured over him, and a man poured it over his head and back from behind. He did that to him, then Sahl got up and joined the people and there was nothing wrong with him. Classed as sahih (authentic) by al-Albani in al-Mishkat.
My question is regarding a different case. Majority of the time, we do not know who the perpetrator of the evil eye is. In such a case, if it is suspected that someone is suffering from the effects of the evil eye, can the parents of the afflicted person give him Ghusl water? Additionally, can we request a pious Muslim to give Ghusl water to someone believed to be affected by the evil eye? Are there any authentic ahadith (like the one in the link above) regarding parents giving their children Ghusl water and/or asking a pious Muslim for ghusl water to ward off evil eye?