Help! Book writing.

(Disclaimer: No, I don't plan on killing myself) I'm trying to write a book and I was really curious about what the quickest and most silent way to take your life would be. Like excluding a gun or a noose. I'm trying to write this scene out to be very mild in the sense that they don't plan on going out with a bang (no pun intended) and they just want to quietly go. I'm having trouble finding ways to write that.