Is it permissible for a fast-food restaurant owner to operate during the month of Ramadan by only delivering external orders, taking into consideration the high rent of the restaurant and employees' wages?

It is not permissible to sell food during the daytime in Ramadan, neither to a responsible Muslim nor to a non-Muslim, except to one who has a valid excuse for not fasting. There is no justification for violating the sanctity of Ramadan's daytime, for provisions are predetermined. Allah, the Almighty, says: "And there is no creature on earth but that upon Allah is its provision, and He knows its place of dwelling and its resting place. All is in a clear register."