If you travel to Iran, then be sure to check the dates beforehand. In the month of Ramadan, a trip to the Iran gives you only limited cheerfulness. Ramadan is the month of fasting, when the believers morally restrain from eating and drinking. As Ramadan belongs to Islamic calendar (different form Iranian calendar-see the section calendar in here), its dates changes constantly and is not fixed, be sure to check it out beforehand. The regime becomes more strict than usual. Who smokes or eats in public during Ramadan and is caught by the police, and may be fined.
As a traveler you have the Tourist bonus, and besides a warning, not much should happen, In addition, the food stalls and restaurants do not sell freshly cooked food during the day. And in public even sipping a water bottle is forbidden. This can cause a bad mood.