If he does not serve tea and coffee to his bosses who are not fasting, they may fire him from his job

Firstly:

It is not permissible to break the fast during the day in Ramadan, except for one who has a valid reason, such as one who is sick, one who is travelling, or a woman who is menstruating or bleeding following childbirth.

Deliberately breaking the fast during the day in Ramadan for no valid reason is a major sin.

Adh-Dhahabi (may Allah have mercy on him) said in al-Kabaa’ir (p. 64): It is well-established among the believers that whoever fails to fast Ramadan without being sick or having a valid reason that allows him to break the fast is worse than an adulterer (zaani) or drunkard; in fact they doubted his Islam and thought of him as a heretic. End quote.

Ibn Hajar al-Makki said in az-Zawaajir ‘an Iqtiraab al-Kabaa’ir (1/323): Major sins no. 140 and 141: not fasting on any day in Ramadan, and breaking the fast by having intercourse or otherwise, with no valid reason such as sickness or travel. End quote.

See the warning to one who deliberately breaks a fast in Ramadan, in the answer to question no. 38747.

Secondly:

It is not permissible for anyone to offer food or drink to someone who he knows will consume it during the day in Ramadan with no valid excuse, because that comes under the heading of helping him in sin and wrongdoing, whether he offers it to a Muslim or a disbeliever. The command to fast is addressed to the Muslim, and he is disobeying Allah by breaking the fast; enabling him to consume food and drink during the day in Ramadan is helping him in sin and transgression. The command to fast, and all other Islamic rulings, are also addressed to the disbeliever, but before complying with them he is required to utter the twin testimony of faith (shahaadatayn) and enter Islam. On the Day of Resurrection, the disbeliever will be punished for his disbelief and for the commandments of Islam with which he failed to comply, so his punishment in the Fire will be increased.

An-Nawawi (may Allah have mercy on him) said: The correct view, which is that of the senior scholars and of the majority, is that the commandments of Islam are also addressed to the disbelievers, so silk is forbidden for them as it is forbidden for Muslims. End quote from Sharh Muslim (14/39).

It says in al-Mawsoo‘ah al-Fiqhiyyah (9/211, 212), under the heading: Selling items that are intended for the commission of unlawful deeds:

The majority (of scholars) are of the view that anything that is intended for unlawful purposes, and any action that will lead to sin, is haraam. So it is not allowed to sell anything that it is known that the purchaser intends to use it for purposes that are not permissible…

An example of that according to the Shaafa‘is is selling narcotics to someone who it is thought will use them in an unlawful manner, or selling wood to someone who will turn it into a musical instrument, or selling a silk garment to a man who will wear it when there is no case of necessity (that would make it permissible for him to do so). That also includes selling weapons to evildoers and bandits.

Ash-Shirwaani and Ibn Qaasim al-‘Abbaadi stated that it is not permissible for a Muslim to sell food to a disbeliever, if he knows or thinks it most likely that he will eat it during the day in Ramadan, as was also stated in a fatwa by ar-Ramli, who said:… Because that is helping in sin, based on the fact that the more correct view is that the commandments of Islam are also addressed to the disbelievers. End quote.

So what this worker must do is fear Allah, may He be exalted, and not help his bosses in sin; he should refuse to serve them coffee and tea during the day in Ramadan – so long as they have no valid excuse for not fasting – even if they order him to do that, for there is no obedience to any created being if it involves disobedience towards the Creator. There are many means of earning a living, and the stores of Allah are full; whoever fears Allah, He will protect him, and whoever gives up something for the sake of Allah, Allah will compensate him with something better than it. So let him put his trust in Allah, and let him tell his bosses that it is haraam to break the fast, and that he will not help anyone to commit that great evil.

 And Allah knows best.