living in Greece, I can persumme that more than 1.000.000 Greeks eat "gyros" every day. From old people to small children. If eating "gyros" was the only cause of stomach suffering, Greece would be a place of agony every night and I know it isn't, not by that kind of agony any way. May be the deep down reason of your stomach problem was the "thing" you tried to choke and shallow with every bite you took, the "thing" that left you unsatisfied and made you look for preasure in a tastefull meal. Probably some"thing" that your inner state detested and denied by punishing you all night long.

Furthermore you searched for temporary "cocacola"relief  when the only thing you had to do is keep walking on and on and put nothing else in your stomach, not even water until you get read of everything "bad".