Some people thrive for decades (including Stephen Hawking) tube fed with nutritionally complete enteral formulas. Semi-annual blood tests pick up any deficiencies, and supplements are added if needed. Several companies make "Soylent", the one I am familiar with is Abbott Nutrition.
If there's something there that isn't priced for sale to hospitals, or restricted in sale to hospitals, and has been formulated so as to be edible by people who are tired of real food, go ahead and post it. My understanding is that tube-feeding is not the same use-case as Soylent at all, with tube-fed material needing to be essentially predigested and correspondingly expensive or something along those lines, and no concern for edible taste for obvious reasons.
I've done some looking, but I haven't seen anything out there that looks like it's meant to be eaten, meant to replace food, and priced at an affordable level for sole consumption.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.