Do foreign citizens need Turkish will ? 
If you are a foreign citizen and have a property in Turkey,  you need to make a Turkish will. 
As properties in Turkey are bounded with Turkish Laws, foreign countries wills and wish letters are not valid for properties in Turkey. 
Then the inheritors should apply to Turkish courts and prove themselves as legal inheritors to obtain heir certificate. There will be court case trials. 
That is a very long and expensive legal process for foreign citizens. 
If you want to make your inheritors comfortable, you need to have a Turkish will for properties in Turkey.
I have explained how foreign citizens make Turkish will.