Ramadan started on 6 June and will end on 5 July. Ramadan moves through the calendar year because it is based on the Islamic lunar calendar year, which is 10 or 11 days shorter than the solar year. As we are in June that means that people fasting for the required dawn to sundown have a very long day without any food or drink. If you employ observant Muslims you need to bear this in mind. It may have health and safety implications, as the employee has not eaten or drunk for a long time by the end of the day.
Even though they have chosen to fast, because it is part of recognised religious practice, a Muslim employee is entitled to fast during Ramadan without negative consequences for them, even if it has an effect on their work. Under discrimination law, in The Equality Act employers should not treat an individual less favourably than someone else with a different religion or belief, so to treat a Muslim worse because they are a Muslim would be unlawful. More likely to be relevant to Ramadan considerations, is that employers are also not allowed to have procedures or practices that have an adverse effect on a group like Muslims. So for example if performance dipped because of fasting, care should be taken with any negative consequences for the employee.
It is considerate anyway to think about the effect on a fasting employee of others eating and drinking around them at work. There may be nothing you can do about it and they may not mind, but maybe they should be asked. You may want to offer temporary flexibility on hours, for example so that lunch is missed and they finish early instead. If you have Muslims on night shift you may need to allow time for eating while they can. If it can be avoided such employees should not be obliged to deal with events that involve food and drink, like business entertaining or trips away.
Ramadan ends with the Eid-al-Fitr celebration, so anticipate a request for holiday then and see if you can allow that. As it is part of religious observance, you should allow it if you can.
If you are affected by Ramadan at work and are in doubt about how to deal with that, please contact me and I can give practical advice on what you are allowed to do.