Question - Most harmless / painless / quick way to kill yourself?

Not a cry for help, just in theory.
Imagine what you would consider ok. If it helps imagine you just didn't want to exist or you were in great pain or needed to escape people from mutilating you.
Doesn't have to be danger based but almost scientifically most easiest DIY way without too much blood?

Soldiers had a pill to avoid being tortured but I guess something more to hand for average person is what I'm thinking... nothing what a person could do on their own almost.

List of some ideas I'm not sure about:

- car in garage (smoke inhalation)
though maybe it is painless not sure

- sword to chop neck / head but how to do that yourself and not need someone else!
(lol, msybe some rooe contraption?)

- hanging by rope (probably best but seems uncreative and 'too' primate!

- Injection (again something too specialist unless apple juice in the artery would do it!)

***Must be a more clever-basic way!***