Back in the day when I was issued mess tins food- cooking out in the boonies for the use of (1982-88), the worst thing was scrubbing the bastard hexamine fuel block residue from the outside. Even back in the day most rations were cookable in their tins so the mess tin was mainly used as a boiling vessel. Either that or put the ration tin on the exhaust manifold of the Land Rover or FV432 as a heat source.
I have tales from my father (RAF 27 years, encompassing said period) of eating those tinned sausages in lard cold, because there was no time to cook them
My favourite from my time in the air cadets was the mixed fruit pudding and the oatmeal blocks.
A proper case of the noms there
Especially the oatmeal blocks- digestive biscuits with attitude.
Personally, I loved the sachets of rolled oats- add a sachet of milk powder, a sachet of sugar (big compo sachet, not your girly coffee shop table sachet) sufficient hot water and neck it before the stand too call comes.
Another good thing was having chocolate Ovaltine in your pack for when the Mars bars were well past their best- i.e. gone white and crumbly. Knock up a black water bottle mugs worth of choccie Ovaltine or other hot choccie mix, cut mars bar into chunks and melt into the mix whilst heating. Another nom fest.
Also, having a jar of Mamrite in your pack. Spread on the garibaldi bisquits that came in the rations. Nomalicious.