All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
There is evidence that the disbelievers are ordered to perform the Islamic rites like: prayer, Zakah and fasting, etc., and that they will be punished for refusing to perform them. Allaah says (interpretation of meaning): {"What has caused you to enter Hell?" They will say: "We were not of those who used to offer their prayers.}[74: 42-43].
Also, Allaah dispraised the people of Prophet Shu'ayb for disbelief and injustice in measuring and weighing. He dispraised the people of Prophet Loat for disbelief and homosexuality and the people of 'Aad, for disbelief and severity in tyranny and intrepidity. Allaah says (interpretation of meaning): {"And when you seize, seize you as tyrants?}[26:130].
The scholars mentioned this as well. An-Nawawi said: 'The chosen opinion in this matter is that the disbelievers are asked to perform the different obligatory rites of Islam and avoid the forbidden ones. This is to increase their punishment on the Day of Judgement.'
If this rule is established, then know that it is unlawful for the seller to sell anything that he knows the buyer will use in committing a sin.
Imaam Ibn Hajar Al-Haythami was asked: 'What is the rule of selling perfume to a disbeliever when you know that he will put it on his idol and selling an animal to a disbelieving enemy when you know that he will kill it without slaughtering in order to eat its meat? He replied: selling is forbidden in both cases. Perfuming the idol and strangling an animal that is going to be consumed are both major great sins even for them, as the disbelievers are required to apply religious obligatory rites just like Muslims. So, it is unlawful for Muslims to sell them what can help them commit a sin.'
From this, you know that the disbelievers are ordered to fast even if it will be rejected because of their disbelief. So, it is forbidden to help them and it is unlawful for you to present food to them during the day of Ramadan.
Allaah knows best.