If your job gave you a surprise three day paid break to rest and recuperate, what would you do with those three days?

I would probably work on my personal project.
Having three, mostly full days, to work on that rather than in the company I work for means that I can get a lot done on my own project!
I would still do the other things I would normally do during those days like going to the gym, but instead of working around 8 hours a day for someone else's company, I would work those 8 hours each day for my own personals goals.