Well, most of what I write here will probably be crowded out with vague, "hardcore" advice such as:
"Suck it up."
"If you're really serious, you'll make the time."
"I worked 80 to 100 hours per week during residency/embarking on business venture and still found the time, even on minimal sleep."
I guess it's all fine and dandy if you can work 80 hours per week while still maintaining the Spartan existence of a serious or competitive bodybuilder.
But for those that can't (which is 99% of people) because burning the candle at both ends is an exercise in futility (correct phrase?) that winds up with no good outcome, you can face the facts that you don't earn an income from bodybuilding and that you're livelihood is more important than your muscles for the time being and that because your venture warrants little sleep and causes you to eat haphazardly, you can go on a maintenance program while you work on your business.
By the way, what mature adult would think you're an idiot because you want to earn an income and realize that your income is more important than muscles (which it should be). No income --> no food, shelter, or gym membership --> no muscles.
Yes, full body routine with a few sets per muscle group, twice per week, is enough to maintain. But you must have the mindset that this is temporary and your ONLY goal in the gym is to maintain.
Maybe something like this:
Deadlift or RDL
Pullup or pullover
Dumbbell bench press
Some warmups and 2 sets of 6 to 12 reps (most likely will need little to no warmups for "smaller" exercises.)