Personally, I find if I've got a very clear road ahead of me with few complex decisions, I can just steam ahead, maybe for 12+ hours with few distractions. However, when it gets into the weeds, it's harder to keep going like that. Spend a little while thinking, have a break, read the latest tech news, walk around a bit, come back, think some more - eventually figure out the answer. I could fill that time with busy work, but I personally feel that I find a better solution if I have some room to think.
Procrastination is definitely a thing too, and it can be hard to stay motivated when the feeling of progress is so non-linear and lumpy. It can feel like nothing is being done for weeks at a time, then suddenly everything fits together.
Meanwhile I have no issues doing, say, physical gardening work. Can spend hours digging, weeding, building planters. Lots of time between decisions to think about what you're doing next and simple, linear, visible progress throughout the day.
On a serious note, I've also been nearly burned out by these week-long take home assignments which are only one stage of several and end up eating my weekends completely only to find myself rejected or ghosted after completing them (I'm a penetration tester so most common candidate testing methodology I've seen is a week long CTF set up by their security team, where you need to find as many flags/vulnerabilities as you can and also write a report, so it always ends up into a huge time sink of finding needles in a haystack and also write a multi page report about how I did it, only for then to be rejected). Often there's also some IQ test and other nonsense stages, plus the usual Zoom/Teams/Meets calls in between with their recruiters/hiring managers, during working hours. Oh, and don't get me started on the 20 page online form with 50 questions some companies want you to fill as part of your application.
I honestly have no idea how people with full time jobs who can't slack off at work and have other responsibilities, hobbies and interests, are able to keep this up. I feel like these long and stressful interview processes are mainly geared towards ambitious new-grads or people with no other goal in life than always interviewing for the next best job.
I sometimes want to give up on the IT industry and go to med school instead as I don't see how I can keep this up long term, for the grand sum of €50K/year, if this interviewing process is the norm or if it will get even crazyer. Or maybe I should quit my job, start learning leetcode, and move to a country with some FAANG jobs.