Anyone offering a single, specific "best" way to rest is likely to be committing the typical mind fallacy. For example, there are people - extroverts - who "unwind" after a work week by going out to clubs. As an introvert, I have a knee-jerk inclination to suspect such people of genuine insanity, because such an activity would have no relaxing or energy-restoring effect for me. Of course, they are no more insane than I am, just psychologically different, but those differences can have a big impact.
As wgd suggests, you can experiment to figure out what is most relaxing for you. Another possibility: if you could provide more details about your own psychology, people who identify with those details could offer their preferred methods. Without more information, I think we will just be other-optimizing.
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.)