All of those, but I also put on some good music or I put on a documentary or another tv programme I might enjoy. Keeping your brain stimulated really helps. (I also listen to Radio 4 online)
I often push myself to finish just a section and then have a proper break for a hot drink, a snack and maybe a half-hour of tv.
As I have no contact with the outside world except via the internet, any tv watching is strictly voluntary - I know exactly how long a programme will last, I can choose to spend half an hour watching a cooking show or something if I like, with my coffee and a sandwich!
On the other hand for marathon work sessions I really miss having a proper television that can be left on in a corner 24/7, with no need to keep choosing "good" things to watch. Really good tv is wasted when you are concentrating on working! But it provides something to rest your eyes and brain on every once in a while, keeping you from getting too tired.
It seems somehow that actually a big part of the "tiredness" is your brain getting fed up with looking at the same things and thinking about the same things. A little bit of variety helps a lot.
Lately it's been music a lot of the time. Good for creative thinking.
Ideally I would have all three, and someone to bring me drinks and food at sensible intervals!
Oh, and smoking a joint really helps. Am I allowed to say that here? The longer the session the more painful it can get, and these things help stamina. If you have been awake and working for almost a solid week with a few naps, the only effect something like that has is to make it hurt less.
I am really finding that being in an isolated environment without the usual types of stimulation (tv, friends, smokes) is seriously affecting my productivity.
Now I will expect to be slated. But I am absolutely serious. We are all different and I'm just answering your question honestly.