The best - the first time I had fresh food in nearly 4 months after living off MREs while on ops. I had to go to a meeting in the ACHQ and had a couple of mates working there whilst I was up in Baghdad and they had the decency to take me out for dinner in downtown Doha. To eat something that actually had a shelf life and not a half life was heavenly and did wonders for morale.
The worst - at the end of that same tour when we had to fly out of Basrah. The Movers were totally unprepared and the only food that was available was a half frozen box of those god-awful sausage rolls. You know the ones - if you sent them off to a lab for testing the results would come back as unidentified. Well not only was there not any food, but no facilities for defrosting the sausage rolls other than turning the barco boilers up to full and propping the sausage rolls up around the outside in the vague hope that you wouldn't shatter a tooth when you bit in to it. They say war is hell, that was the damned worst moment of entire war for me, certainly the one that carried most risk.