Best price I found was at the KFC at Dalaman Airport. 11 Lira for a can of Efes.
Worst we saw for soft drinks was at the beach down the road from the Ghost Town. We took the offer of a 'free' sunbed then got the bill for our drinks. 4 Lira a can for Coke/Fanta and then 10 Lira for a pancake. Nothing is free.