Right now in Turkey it is Ramadan. It began while I was in Antalya and I was wondering how it would affect tourists in Turkey that are not Muslims. The answer is that there is little effect at all.
People partaking in Ramadan do not eat between sunrise and sunset. During this time they fast by not eating or drinking. At least in the places I have visited, it does not seem to be heavily practiced. Most restaurants are open and many Turkish people are eating lunch and dinner.
The more interesting part to me though was the nightly and early morning announcement that remind people they can now eat. People go down the streets banging a drum and making lots of noise at sunset and, perhaps more importantly, just before sunrise at around 3:30am, to wake people up so they can eat before the sun comes up.
Depending on where you are staying during Ramadan, you may get woken up at 3:30am with the banging of a drum. You may want to choose a higher floor or a more soundproof room!