I have no idea. I found that really good isolating headphones, listening to a 15-minute electro track, and just laying on the floor breathing deeply has been more restful than the average 15 minutes recreation.
Also side projects learning something (recently code) seem to vitalise me.
It might just be because I have ASMR, but watching YouTube videos of medical examiners describing examination procedures is extremely restful / re-energising for me.
So, it's well-known (or, at least, oft-thought) that you can't just work 16 hours a day; if you want to get stuff done, you need to rest from time to time. You have to take breaks.
Today, just now, I realized that I don't really know what the best way to rest is. If I want to rest, should I do something that's fun and interesting, like reading a fantasy novel? Should I do something that's boring, like building roads in Minecraft, so that work will seem comparatively interesting when I get back? (And besides, reading a fantasy novel is a bit of a challenge, at least for me, whereas building roads in Minecraft is trivial.) Physical activity probably helps, but how much? Do relaxing activities, like taking a warm shower, help more than just sitting there? How can I tell when it's time to take a break? How can I tell when it's time to get back to work?
(Suggestions for tags would be appreciated.)