I went hiking today and brought a cold bag for beer and a warm bag for foil-wrapped hot dogs. I put two hand warmers in with the dogs hoping they'd keep warm but opening them up at the summit 2 hours later I was disappointed to find lukewarm dogs. How do you deal with keeping food hot for a few hours on a hike? Weight is a secondary concern since this is only for day hikes, though a foil wrapped brick probably isn't ideal