Back in the 80s my wife found small cartons of irradiated milk. It did not have to be refrigerated.
I took them on my Field Training Exercises that usually lasted four days. They were a bit heavy but a nice change from water and powdered coffee.
On board ship, they served the stuff ice cold out of a big dispenser, I drank so much of it, I actually started liking it better than fresh milk.
It has to be ice cold though.