“RIPPED OFF”

Yesterday I travelled home via Palma airport. I bought 3 coca colas which cost 350 pesetas each. This is, of course, very expensive compared with outside. The drinks were not only warm but did not taste at all like coca cola. I think, in fact, that it had been watered down. I object to being ”ripped off” like this and I wonder how I could make a complaint to the airport.
Are you able to help ?

David Kerr