what I normally do now is drink my bottle of water before security and keep the empty bottle then I put a bit of tap water in just enough to see me through until I can buy a bottle on the plane, which even though expensive (we have found Easyjet to be a bit more sensibly priced!) I used to do the same as you Phil and count out all my loose change but then I begrudged handing that over in the end, not because I was being a tight a**e but the principal of a 50 kourus bottle being sold at a stupid price...
I realise my method would not be suitable if you had children with you or the intense heat of August but I have gained a little satisfaction the last few years by not purchasing any water at Dalaman

apologies for going off topic but this should be my 2500th post yah