Is it permissible in Islam to sell food which is halal to non-Muslims and these non-Muslims believe that if they eat or drink that food they will be saved from any harm and they will be rich and so on (Shirk Deeds)and also for ritual offerings, when we know very well when we sell that food to them is only for that purpose.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Your question comes under the issue of selling something that leads to what is haram is itself, wether this is forbidden or not. The jurists give as an example: selling grape to one who will use it for making wine, and they differ whether sales for this purpose are valid or not. Here are their opinions:

1- The Maaliki and Hanbali Schools of jurisprudence, and the correct opinion of the Shaafi'i School, state that it is forbidden to sell grapes to someone if we are sure or we predominantly think that he will use it for making wine. But, if the seller has doubts in this concern, then it is only disliked.

2- According to another opinion of the Shaafi'i School of jurisprudence, it is disliked, although the sale agreement is valid in both cases.

3- Abu Haneefah is of the view that it is permissible, i.e. to sell grapes to those whom one knows that they will use it to make wine.

However, the dominant opinion is that of the majority of the scholars: such selling is invalid as long as one is sure that the purchaser will use grapes to make wine, or even if it seems that likely it will be used for such a thing, since the means have the same ruling as the ends (objectives). In simple words, every means that leads one to commit what is forbidden is in itself forbidden.

Allah Says (what means): {And cooperate in righteousness and piety, but do not cooperate in sin and aggression.} [Quran 5:2]

Allah knows best.