It depends on what you mean by best. For me, best means least painful. I'm in the same position right now with no SN, N. From spending a lot of time reading, I think the least painful would be partial suspension/night night or an opioid overdose.
If you read accounts of people who have been blood choked in martial arts (compressing the carotid arteries as you would in partial suspension/night night) or of people who have survived opioid overdoses, they say it's painless (though perhaps uncomfortable in the case of blood chokes) and weren't aware of when they blacked out.