If you're asking what I'm doing with my time, spending way too much time on Bluelight, lol. Which is probably not the healthiest choice but it does make me feel like I am helping others at least.
But if you are asking what I would recommend I would say anything that you enjoy, that makes you feel good/healthy, that makes you feel useful or that helps others. Any hobbies or interests, getting outside, exercise, volunteering, reading, spending time with other people, all that kind of stuff. I liked herbavore's suggestions. I highly recommend yoga. Anything that is working on improving your life or mental health is great too. Getting re-connected with nature is very important IMO. And maybe connecting with your ancestry or indigenous peoples. I've been going to native healing ceremonies and have found that very helpful. If you are going to watch TV or read I recommend non-fiction and documentaries. Listening to or playing music or singing are hugely helpful IME too.
EDIT: I'm going to try to be better at taking my own advice. Maybe I will get off the computer and do some cleaning and get some fresh air. It's very easy to replace a substance addiction with a behavioural addiction, like spending a lot of time on the internet, playing video games, or watching TV. Although in the short-term that is probably a lot healthier than doing addictive drugs, it can still become an addiction that gets out of control and adversely affects one's life.