Drinking water Water from the tap is for use, like for washing, you should not drink it. To have drinking water - I recommend the bottled water. This water is good quality and you can find it in any grocery shop. Always carry a bottle of water with you whenever you are sightseeing. Good bladder control is often a great thing in Turkey.
Public toilets are few and far between.
Your best bet to find a clean rest room is in a restaurant or hotel. The bottom line is don't drink too much and go to the bathroom whenever you find a good one even if you don't have to. Turkey has the largest NATO force after America - and I think that makes them feel close to us. You will be very respected and loved. The food is delicious and nothing will happen unless you eat too much.