Praise be to Allah.
With regard to any waqf (endowment) or donation that is given to the mosque – or any other cause – it is to be handled and disposed of according to the conditions stipulated by the one who set up the waqf or who donated it.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:
What is required with regard to anything given as a waqf is that people should dispose of it according to the conditions stipulated by the one who set it up.
End quote from Fataawa Noor ‘ala ad-Darb (16/2).
Based on that, the one who sets up the waqf may benefit from this waqf that was set up for the benefit of the public, like any other Muslim, without benefitting more than an ordinary Muslim would benefit. So he may drink from it as they do, and benefit from it in other ways like other Muslims, so long as he did not stipulate any other conditions apart from that.
‘Uthmaan (may Allah be pleased with him) designated a well in Madinah as a waqf, and he used to drink from it as other Muslims did.
At-Tirmidhi (3703) narrated from ‘Uthmaan (may Allah be pleased with him) that he said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Who will buy the well of Roomah and drink from it as other Muslims do, in return for something better than it in Paradise?” ‘Uthmaan said: So I bought it with my own wealth. Classed as hasan by al-Albaani in Saheeh at-Tirmidhi.
Ibn Hajar al-Haythami (may Allah have mercy on him) said:
The words concerning ‘Uthmaan’s waqf of the well of Roomah, “drink from it as other Muslims do”, were not a condition; rather they indicate that the one who sets up the waqf may also benefit from his waqf that he sets up for the benefit of the public.
End quote from al-Fataawa al-Fiqhiyyah al-Kubra (2/275).
Ibn Battaal (may Allah have mercy on him) said:
Whoever designates a well as a waqf to provide drinking water, there is nothing wrong with him drinking from it, even if he did not stipulate that, because he is included among those for whom drinking water is provided.
End quote from Sharh Saheeh al-Bukhaari (6/492).
Al-Bukhaari (may Allah have mercy on him) said in his Saheeh (4/7):
Anyone who dedicates a camel or something to Allah may make use of it as others do, even if he did not stipulate that. End quote.
Based on that, whoever donates bottles of water to the mosque, that is intended for the worshippers in that mosque. In that case, the donor is one of the worshippers, so it is permissible for him to drink this water, just like others.
The same may also be said with regard to perfume. If he donated it for the worshippers to use, then he may also use it, like any other worshipper.
And Allah knows best.