Given that cryonics is currently essentially just a scam, you might just as well. For all practical purposes, it's equivalent to killing. (Legally, you need to have just died though, in most Western countries, so I think you don't actually have this option.)
https://bigthink.com/the-future/cryonics-horror-stories/
Or you meant just traveling there, going on an extended hike from which you don't return because you just purposely one day didn't get out of your tent. That's not a pleasent way to die though, and nobody is going to go there 300 years from now to unthaw you.
> - If none of that is possible, do something interesting and dangerous. For example, if my brain is going anyways, experimenting with drugs and dying by drug overdose seems like a decent way to go.
How do you know that a drug overdose is a pleasant experience? You could be hallucinating the most terrible things in the world for as it may feel like an eternity. Unless you are talking about sleep medication, but then again, just taking a bunch of sleeping pills is not different from a "classical" suicide.