What is the ruling on giving a forged food recipe to a person who has not eaten in my restaurant, to enable him to obtain a free meal from his company?

If your brother asks you for proof of a meal he ate at your restaurant, when he did not, this is forgery and forbidden deception. It is not permissible for you to do it, nor to assist in it, for the Prophet, peace and blessings be upon him, said: "He who deceives us is not of us," and "Cunning and deceit are in the Fire." You must prevent him from injustice and explain to him the unlawfulness of his action, for that is supporting him.