A Senior Developer working mostly with PHP and JavaScript, with a bit of Python thrown in for good measure, all on Linux. My tooling is simple, it's GitLab and JetBrains where possible.
Some of these are things people have already suggested, but here goes:
Water - keep yourself hydrated. I've been dieting for the last week, and as part of that I've been drinking far more water than normal. I feel better for it.
Nutrition - have a variety of meals rather than the same things all the time. This can get difficult, but changing a couple of ingredients can mean the same "boring" food gets a new lease of life.
working environment - make sure you have your workspace set up right. Monitors are eye level so you aren't looking up or down. Have a wrist rest for your keyboard if you need one. Get an ergonomic mouse if required. And make sure you invest in a decent chair. You're going to be in it for a lot of time.
Exercise (I don't do this remotely close to enough) - something as straightforward (for most) as walking can be hugely beneficial. You don't need to go and run 10k each day, just get out for some air. On top of that, making time to stretch each day so you don't get muscle tightness from sitting inactive
take a look around - staring at a screen all day isn't great for the eyes. Nor is averting your gaze to look at the wall which is 6-inches behind it. I've recently rearranged my home office so I can look up and look out of the window. The difference in being able to look so far is resting my eyes so much more. And I get natural light when I want it.
Avoid energy drinks - this is coming from someone who used to have one a day, as well as coffee. They are loaded with all kinds of additives, even the sugar free ones. They are awful for your teeth and gums. Save them for the 24-hour hackathons when you really need the stimulation.
sleep - make time for it, and get what you need. Some people need more than others. Some are 3-hours a night, some are 9 or 10 hours a night. I know that I need at least 6.5 hours to have a good day. Much more than 8 is usually too much for me.
take a break - this is both during the work day, and after. Don't sit glued to your computer or other devices. Make time for the exercise, or a hobby which doesn't involve a screen or...
social interaction. It's a great stereotype that developers are loners who would, if they could, avoid all contact with anything resembling humanity. The reality is we are human. We are social creatures who need some level of interaction. Just talking to somebody to build some connection is, chemically speaking, good for us.
There's so many other things which could go on this list, but remember not just to focus on your physical wellbeing. Mental health is just as important. Possibly even more so, as if you're in a bad place mentally you may not feel the need to look after yourself physically. Mental health is overlooked far too often, which can lead to awful consequences for all involved.
Some of these are things people have already suggested, but here goes:
There's so many other things which could go on this list, but remember not just to focus on your physical wellbeing. Mental health is just as important. Possibly even more so, as if you're in a bad place mentally you may not feel the need to look after yourself physically. Mental health is overlooked far too often, which can lead to awful consequences for all involved.
Great answer in detail. Thank you