Focus when you’re not focused?

What I usually do is set time goals instead of tasks goals and start working, slowly, with no pressure. After each working period, I do a little break and then go back to work. I do not focus on the outcome but in working, and slowly I start to get momentum. I think the most important thing is to be gentle with yourself and not be very demanding, just try to work no matter how productive you are. Slowly your focus will be coming back.

It helps to just get something done, even if it's one percent of the task at hand. I think that's really how to get things rolling.

And then if you're struggling to stay focused when half way through, I think it's nice to challenge yourself to finish the task at hand before getting up to get that can of La Croix or whatever it is you want to do other than the task at hand.

Do not push for it. If you struggle focusing, you are most likely exhausted.
To maximise your focus time, try to find a rhythm of regular focus phases and breaks(!). Wether that is pomodoro technique or something else, you need to do rest regularly and recharge your batteries.

Strange enough, when I am tired, I get the best focus. So when I sleep really bad, the day after I am too tired too look up funny stuff, get lost in bike shedding blogs or code experiments. Instead, I just want dumb work and on those days I get done the most. And - in case you wondered - quality does not really seem to suffer from it, because when I look back on it later, I don't feel the need to re-do it.

So I guess the recipe for me should be to stay up late ...

I personally follow 50:10 strategic to keep up the focus, Do 50 min of work and give a 10 min break.
It worked for me to keep focusing, Give it a try .

I force myself to take the dog on a steep and long walk for an hour or so while playing super loud and obnoxious deathcore from a bluetooth speaker (my neighbors adore me) which is a whole journey that forces me out of the frame of mind I am stuck in naturally and when I get back I am tired enough to sit and work but not too tired that my brain is totally dead. Especially late at night with all the mountain lions around here, see a panther and I guarentee you'll have a significant head change sufficient to break through that fog.

I DO NOT TIME MYSELF, for me it makes me a nervous wreck and I never enjoy those breaks very much or get distracted during one and BAM! three hours gone. I do not allow myself to be only moderately productive, if I go walk for an hour that's a lot more productive than writing 3 comments and tinkering with the layout slightly for 4 hours. One hour lost walking, 3 gained not trying to force myself to kick over into my beserker productivity mode. BUT THAT'S ME.

Also I keep NoDoz and Bronkaid around for those really stubborn fogs, a little stimulation goes a long, long way if you know what you are doing. Got me cum laude in undergrad with only 2 hours of sleep a night and a full time job, so it does work but its honestly not as effective as forcing myself to trek about the East Bay hills with my dog and the sounds of Hell coming out of a speaker.

Take a nap.