If you're not drinking their water untreated, then don't accept ice in any drink.

Ditto for water you use for brushing your teeth. When I was in Sudan I stuck to water I boiled myself, CocaCola and hibiscus tea they call kharkadeh or something like that. Then, after two weeks or so, I discovered how that tea was made: one brews dense syrup few times a week, then grabs a bucketfull of Nile water and dilutes it as needed.... I had absolutely no digestive problems.

Seriously, I don't think water- and food-borne deseases are something to be very vary of in Turkey. They have quite healthy tourist industry