No you are wrong. In order to get there (build successful brand) you have to take care of your self. With coding marathons, buckets of coffee and fast food (because "I don't have time to cook") you will end up with heart attack before you achieve what you planned.
Not only that but adequate sleep, regular exercise and healthy eating contribute enormously towards healthier cognition. As a developer, I tend to find myself far more productive and successful in a shorter period of time when I am living on the healthy side of things. Everything that is me just works better when I go for a run three days a week, eat clean foods and get in a solid 8 hours of rest a night.
A full time job is a 9-5. Let's say you commute from 8-9 and 5-630. That means you can gym from 645 to 8 (including travel time), eat decently, do some coding, hit bed around 1030, and be sleeping around 11 (so you have enough time in the morning by waking up at 7). Cook on the weekends, code on the weekends, social life Friday and Saturday night...
Do you work more than 40hrs a week? Why? Sounds like you're creating someone else's brand if so.
Let's say you have half of this spare time to work on your side project, that is 3 hours. Excluding weekends, how much time would it take to build a business out of your 15-hours-per-week side project?
Well, typically building a business is a full time job. I'd recommend someone make extra money in their spare time to facilitate a work-break rather than trying to do two "full time" jobs at once.
With exercise, I'm finding cycling to work and lifting weights are effective in terms of time. I spend half an hour of my day getting to work and back - probably about 10 minutes longer than it would take in a car. And with weight lifting, I never do any more than 3 sets of 10. The actual amount of time it takes is short.
This isn't exactly olympian conditioning, but I do notice a benefit and the time investment is low.
The principle is that you have to maintain health.
I think late-night coding is a near-constant because of our brains automatically optimize us onto what pg describes as "the Maker's Schedule". Context switching is anathema to effective coding, so people automatically go to the time when they'll be least-interrupted, which is when the rest of the world is asleep.
You need around 7-8 hrs of sleeping to focus and proper brain functions. Only 3-4% of world people can survive and work perfectly with 4-5 hrs of sleep.
getting 3 solid hours of working on your brand a day is much better than 7 bad ones late at night. Wake up earlier, work at lunch, work immediately when you get home. Late nights are not always necessary.