Praise be to Allah.
There is nothing wrong with that. This was narrated from some of the salaf (early generation), and many of the scholars stated that it is permissible.
Ibn al-Qayyim (may Allaah have mercy on him) said in Zaad al-Ma’aad (4/170) concerning ruqyah to treat the evil eye:
A number of the salaf thought that verses of Qur’aan might be written for him, then he can drink them. Mujaahid said: There is nothing wrong with writing Qur’aan then washing it and giving the water to the sick person to drink. Something similar was narrated from Abu Qulaabah. It was narrated from Ibn ‘Abbaas (may Allaah be pleased with him) that he ordered that Qur’aan be written for a woman who was having difficulty in childbirth, then it was to be washed and the water given to her to drink. Ayyoob said: I saw Abu Qulaabah writing something of Qur’aan then he washed it with water and gave the water to a man who had some pain to drink it. End quote.
Shaykh Muhammad Ibraaheem Aal al-Shaykh (may Allaah have mercy on him) was asked:
Is it permissible to write some verses of Qur’aan for a sick person on a vessel, then wash it and drink it?
It does not seem that there is anything wrong with that. Ibn al-Qayyim (may Allaah have mercy on him) narrated that an umber of the Salaf thought that verses of Qur’aan could be written for a sick person to drink. End quote.
Fataawa al-Shaykh Muhammad Ibraaheem (1/94).
And Allaah knows best.