Sit cross legged and close your eyes. Don't move a muscle. Don't think about anything by completely concentrating on your body. No thoughts and no movements.

Without any thoughts, you'll lose your sense of time. And your body would slowly go to sleep when there is no movement.

When your whole body goes to sleep, you'd either enter the state of super-lucid dreaming, or pass out. Set a 3 hours alarm when you sit.

The person who'll wake up won't be you. But, someone else. That's the fastest way of killing yourself.

Update: This is further explanation to my answer.

The question asked was “What is the quickest and easiest way to kill yourself?”

A person who wants to kill themselves, is inspired by the subtle thought that “I can't live with myself anymore”. So, with the “I” being the body, and “myself” the person, this answer gives the easiest way for the person to die.

The person here, is what you identify with as “me” or “myself”. And it's basically a collection of feelings and thoughts that you identify with.

When you break your thinking pattern, the thought energy or emotions that you have, also change. Emotions or feelings are reaction of your body, to your thoughts.

When a person succeeds in remaining thoughtless and motionless, but aware for as long as I've described, an inner peace, tranquility and resultant inner joy is born within them. One can no longer go back to being the same person who wanted to kill themselves. Hence, the old person is dead.

This is the process of coming more in touch with “being” or “living”. The person dies, while the human “being” arises once again, who is capable of handling all kinds of hardships, without ever feeling any mental agony or suffering.

Have a good day, and message me if you'd like to talk. :)