Those are lifeboat rations. There are several brands. Datrex, Mainstay, Mayday, SOS, etc. Another to look into are Millennium bars. They are basically the same thing, only packaged in smaller servings and they come in a wide variety of flavors.
I use Datrex along with MRE peanut butter and cracker packs as my short term BOB food and it works very well. I did a number of full out test bug outs over several years, and my BOB food philosophy evolved rather quickly. I went the full gamut from camping meals, to store bought stuff, but ended up wanting foods that took no preparation and that I could eat while on the move.
I would strongly suggest trying it for 3 days before committing to it in the BOB though. Some brands tend to give some people gastric distress when that's all you eat. I had to switch brands, myself. Though I wouldn't recommend Datrex until they get their packaging issue solved. For a while, some of them were being sent out that had air leaks. I'm sure they have corrected that by now. But there are other brands that haven't had the problem.