Nutraloaf: a bland meatloaf served to prisoners with "behavioural issues". Only problem is you have to go to prison to get it, and it tastes so bad there's been legal challenges against it.
Diet Bars: the problem is they're mostly designed for weight loss or muscle gain, and I couldn't find one that claimed it was good to eat for every meal. CalorieMate and One Square Meal come pretty close, but even they won't claim their product is good for every meal, leaving "dinner" conspicuously absent from their list of "real meals for people on the go".
Liquid Food: things like Ensure, although again these are "nutritional supplements" and not "nutritional replacements". This is close to what you'd get in a feeding tube in a hospital though, which is promising, but again falls into the trap of "gain weight / lose weight / etc" and not "If you drink 500ml of this every 12 hours you will not die any sooner than you would otherwise", which is an advertising pitch left wide open by the market! This is our best bet, however, until we get to:
Tube Feeding: this is literally what you'd be fed through a tube. You can take it orally, though when it comes to this the website says only "May be used for oral feeding of patients with altered taste perception" which is BASICALLY the best way to say "this tastes incredibly terrible" that I've ever come across. This brings us to our best contender:
Multi-Purpose Food: this one has the most promising name, the best packaging design, AND it was made for fallout shelter survival kits and used on humanitarian missions. But the sad news is that it is no longer produced. Seriously, check this out:
I received TONS of email supporting the idea of this easy, convenient food so if you work at General Mills, know this: there is an army of internet people who want to eat your product, especially if you market it as "Multi-Purpose Food". It is 2012 and we are ready for a tin box labelled "Multi-Purpose Food".