Can We Accept Food and Sweets from Non-Muslims?
Question

If a Christian or Jewish person gives me sweets or food or a drink, is it permissible for me to ask whether it is permissible or not, or whether there is pork in it or not? Or should I keep quiet and mention the name of Allah and eat? What I mean is asking one of the Muslim brothers for his opinion about what it contains.
Praise be to Allah.Permissibility of Accepting Gifts from Non-Muslims in Islam
It is permissible to accept a gift from a non-Muslim because he is a relative or neighbour, or for the purpose of softening his heart and calling him to Islam, but it is prohibited if it is done as an act of friendship or love, because Allah Says (interpretation of the meaning):
{O you who believe! Take not the Jews and the Christians as Awliya’ (friends, protectors, helpers), they are but Awliya’ of each other. And if any amongst you takes them (as Awliya’), then surely, he is one of them. Verily, Allah guides not those people who are the Dhalimun (polytheists and wrongdoers and unjust).} [Al-Ma’idah 5:51]
{O you who believe! Take not as (your) Bitanah (advisors, consultants, protectors, helpers, friends) those outside your religion (pagans, Jews, Christians, and hypocrites) since they will not fail to do their best to corrupt you. They desire to harm you severely. Hatred has already appeared from their mouths, but what their breasts conceal is far worse. Indeed We have made plain to you the Ayat (proofs, evidences, verses) if you understand”} [Al `Imran 3:118]
The Prophet (blessings and peace of Allah be upon him) accepted the invitation of a Jewish woman and ate her food.
Al-Bukhari (may Allah have mercy on him) included a chapter entitled “Chapter on Accepting Gifts from Mushrikin”, in which he said:
Abu Hurayrah narrated from the Prophet (blessings and peace of Allah be upon him) that Ibrahim (peace be upon him) travelled with Sarah and entered a village in which there was a king or a tyrant. He (the king) said: Give her Hajir (the mother of Isma`il, peace be upon him). And the Prophet (blessings and peace of Allah be upon him) was given a gift of a sheep containing poison. And Abu Humayd said: The king of Aylah gave the Prophet (blessings and peace of Allah be upon him) a white mule and a cloak. And he quoted the story of the Jewish woman who gave the Prophet (blessings and peace of Allah be upon him) the poisoned sheep.
Conditions for Eating Meat from Jews and Christians
It is permissible to eat meat slaughtered by a Jew or a Christian, subject to certain conditions:

That it be slaughtered in the same manner as the Muslims; so the throat and oesophagus should be cut and the blood should be allowed to flow. If he kills it by strangling, electric shock or drowning in water, then it is not permissible to eat his meat, just as if a Muslim does that, it is not permissible to eat his meat.
The name of Allah should be mentioned over it, and no other name should be mentioned such as the name of Christ or anyone else, because Allah Says (interpretation of the meaning): {Eat not (O believers) of that (meat) on which Allah’s Name has not been pronounced (at the time of the slaughtering of the animal)} [Al-An`am 6:121]. And He Says concerning prohibited things (interpretation of the meaning): {He has forbidden you only the Maytah (dead animals), and blood, and the flesh of swine, and that which is slaughtered as a sacrifice for others than Allah (or has been slaughtered for idols, on which Allah’s Name has not been mentioned while slaughtering)} [Al-Baqarah 2:173]

If it is not known how the meat was slaughtered or whether the name of Allah was mentioned over it or not, it is permissible to eat it and he does not have to ask about how it was slaughtered, because of the report narrated by Al-Bukhari (2057) from `A’ishah (may Allah be pleased with her), according to which some people said: O Messenger of Allah, some people bring meat to us and we do not know whether they mentioned the name of Allah over it or not. The Messenger of Allah (blessings and peace of Allah be upon him) said: “Mention the name of Allah over it and eat it.”
Shaykh Ibn `Uthaymin (may Allah have mercy on him) said:
So it is permissible to eat even if we do not know whether the slaughterer mentioned the name of Allah or not. Similarly, it is permissible to eat even if we do not know whether it was slaughtered in the proper manner or not, because if an action is done by the appropriate people, then in principle it is valid and sound unless there is evidence to the contrary. If we receive some meat from a Muslim or a Jew or a Christian, we should not ask about it and we should not ask how it was slaughtered or whether the name of Allah was mentioned over it or not. It is halal so long as there is no proof that it is prohibited, and this is one of the ways in which Allah has made things easy for us. (End quote from Liqa’at Al-Bab Al-Maftuh, 1/77)
This is with regard to things in which proper slaughter is stipulated, such as animals and birds.
Guidelines for Non-Meat Items: Sweets, Vegetables, and Fish
With regard to fish, sweets and vegetables, there is nothing wrong with eating them, unless it is known that something prohibited has been put in them, such as alcohol or lard (pork fat).
The ruling of prohibition cannot be confirmed on the basis of doubt. But if a person tries to be careful and only eats that which he knows and is certain that it is free of prohibited things, then this is better.
The Jews adhere to the proper method of slaughter, and they avoid pork.
And Allah knows best.