As far as Islamic Shari`ah is concerned, it is permissible to sell food during the daytime of Ramadan. You know the food should be available before sunset time as fasting people need to prepare iftar meal before sunset. Also, there may be people having excuses not to fast (such as ill people or menstruating women or even non-Muslims living in a Muslim country). Therefore, food should be available for those people.

Dr. Monzer Kahf, a prominent economist and counsellor, stated: it is permissible to sell food during the day of Ramadan. Don’t all fasting people need to buy food for use at the time of sunset?

What is prohibited, for adults who qualify for fasting, is breaking the fast by eating, drinking, smoking, or having intimate relations with their spouses during the fasting hours. A food seller must not allow such a thing on his or her premises.
As for persons who are not required to fast (such as ill people or traveling adults or women having their period or children below but close to puberty), they are highly recommended to abstain from eating or drinking in public. This is why restaurants in Muslim countries are recommended to either close or make eating area away from public eyes.