Nothing! I'm super-serious, and I plan on doing exactly that for the following 6 months (quit my job, taking a break to address burnout and reorient): nothing.
By that, I mean I'll allow myself to get as much sleep as I humanly can, try to feed myself healthier food (and more regularly), develop my hobbies (mini painting, playing the bass, sketching, writing), re-establish a semblance of a social life by exploring the city and its options, spending more time with friends... Pretty much just living life. No goals, no quotas, no deadlines, no performance metrics, no side-hustle, no Work™.