It is not permissible for the Muslim to eat foods that the Jews, Christians and mushrikoon make for their festivals. It is not permissible either for a Muslim to accept such things that are given to them on the occasion of their festivals, because that implies honouring them and cooperating with them in manifesting their symbols and propagating their innovations and sharing their happiness on the days of their festivals. That may also lead to taking their festivals as festivals for us too, or to exchanging invitations to meals or to give gifts on one another's festivals at the very least. This is a kind of deviation and innovation in religion. It was proven that the Prophet (peace and blessings of Allaah be upon him) said: Whoever introduces anything into this matter of ours that is not part of it, will have it rejected. And it is not permissible to give them anything on the occasion of their festivals.
Reproduced from Islam QA