I usually bring some cut up cooked meat and a baked sweet potato. Perhaps some steamed vegetables as well. Season it with whatever sounds good. Kinda boring but it does the job. I usually don't have room for much more than that. They make some nice insulated containers nowadays for bringing bowls of warm foods. I have a Thermos Lunch Jar, but I've seen even bigger Thermos lunch containers with split sections and some other container that was like an insulated bowl and came with a detachable spoon. Saw these at CVS of all places. You could put anything hot or cold in there.
The beef sticks are probably not as healthy as bringing an actual steak.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Current squat: 180 x 2. Current Deadlift: 230 x 2