Danube

I'd go on a European river cruise. I'm assuming you are easily fatigued (I am) and I think if you're too tired to do much you can sit on the sun deck and watch the beautiful river scenery, and disembark for tours you have the energy for. The food is fantastic and there are some remarkable cities to visit. For example, in Vienna we attended a concert held in a palace, in the same room where Beethoven previewed his Eroica symphony. In Budapest, we saw a memorial to the jews who were lined up along the Danube, told to remove their shoes, shot and pushed into the river. We went on 8 day cruises on the Danube and Rhine rivers. You unpack once and visit remarkable cities and towns. Upgrade to business class on your flights. You'll be more comfortable.

The other thing I would do, if you have the money (it's expensive) is a Nile river cruise, visiting the new Egyptian museum and other ancient Egyptian sites.

Volunteer your time feeding the homeless (food banks stuff) or at a church that serves meals to the homeless. Volunteer at an animal shelter.

Do you have loved ones? Parents, siblings, nieces, nephews, gf? Write them letters. They will treasure these.

The time you have left is valuable. Spend it doing worthwhile things, not just getting wasted on hard drugs.