I've packed in slices of frozen meat in a Mongolian beef marinade in a leak-proof container (lunchbox with tape around the lid)
By the time it's time to halt, the meat has thawed and marinaded nicely, and it takes no time at all to grill it, the brown sugar in the sauce caramelizing nicely on the meat.
Don't cut the meat too thin, the marinade almost liquefies too thin slices, and thicker slices might not thaw as fast, to prevent spoiling. Also easier to improvise a skewer for a thicker slice if you're not bringing one.
I've also packed in foil-wrapped fish fillets with bacon/chorizo, spices and butter, just bring a lemon or something for once the fish is done.
Unless it's really cold out, I don't imagine either of these will keep beyond the first day if you're doing a multi-day trip.
>>2813386Now there's a memory. We had a single-sized one at home, we'd use it to make toasted sandwiches on the top of the old wood stove when the power went out. For trips, it was foil-wrapped sandwiches on the embers.