Most offices are happy to provide simple water, tea, coffee and snacks for their staff for several reasons.
First, it means that you can provide them to customers and clients when they come to visit the office. Just a simple cup of tea can make a client feel more relaxed and help to get the business done.
Second, it saves times to provide drinks and snacks to staff. If the office does not provide them, the staff will have to leave the office to go and buy them, which of course takes time.
Third, the staff will feel that the company really do value them more highly if simple but essential thinks like tea and water are provided. Staff are more likely to perform better if they think that the company is trying to look after them.
Once you have decided to provide water, tea, coffee and small snacks to the staff you then have to decide who will be responsible for making sure that they are replaced when they run out. You could appoint one person to always be responsible or take turns having one staff member be responsible for one week and then another person taking over.
The company accountant will probably allow the cost of water, tea and coffee out of the company's petty cash. If not you could ask everyone to put in a small amount and then buy the essentials with that money.