Shaykh Muḥammad ibn Hādī al-Madkhali advises that if a Muslim is invited to eat during the day in Ramadan, they should clearly explain that fasting is obligatory and eating is prohibited. They should state this politely, as if they are in a non-Muslim environment.
What should a Muslim say if he is invited for food during the day in Ramaḍān?
It is as though he is in a non-Islamic land. He should say to him, this is prohibited upon us. We are Muslims and we have this month of fasting, and it is not permissible for us to eat or drink. It is upon him to say this and to clarify to them that this is prohibited upon him during the day time.