Is it permissible to eat and drink from the products of the dairy factory where I work, given that the factory manager is the one who brings them to us?

These products belong to an infallible person (Ma'soom), so it is not permissible to dispose of them except with the owner's permission, or by what stands in place of permission, such as custom or condition.

Therefore, if the owner permits it, or if custom dictates it, then it is permissible to use them to the extent that is customary or permitted. Otherwise, it is not permissible to take anything from them, due to the Almighty's saying: "And do not consume your properties among yourselves through falsehood."

Falsehood (Al-Batil) is that which is not with a good heart. It must be noted that permission is only considered valid from someone authorized to give it, and not from any other official.