What is the ruling on eating from restaurants where Hindus and others are responsible for making the sandwiches?

If the food does not require ritual slaughter (like fish and plants), there is no harm in consuming it from the hands of Hindus and others. Similarly, if it is something that requires ritual slaughter, and it was slaughtered lawfully by a Muslim or a person of the Book, then it is permissible to consume it from the hands of Hindus or Majus (Zoroastrians). The criterion is the one who slaughters, not the one who prepares the food. However, if the food is not permissible (halal (definition)) or was not slaughtered lawfully, it is not permissible to consume it, regardless of who prepared or served it.