Also in some cases, you are morally bound to work on the startup when you've recovered and not waste time programming some side project. But too burnt out to code at all.

So, what many do is neither of the above - they read books, play games, have meetings, or some other time filling activity.

Agreed. In my case the side project was preparing 4 months to interview at the big 4 companies, and I interviewed with 3 of them and luckily got 3 offers :)