How do I go to hell?

Solution 1:

It appears you can only go to hell once per game-day. You get the debuff Pooped when your energy is very low(5% of max energy) with a duration matching the time until the next game day, which is every four earth hours.

Solution 2:

Get your energy down to low levels. Then, do one of the following:

• Drink a beer for a energy debuff that takes 35 energy over time.
• Do some No-No Powder, then wait until the rush and the crash wear off.
• Idle at 0 energy. Eventually, you'll croak.

I did notice that, the one time I died, I got to 0 energy almost immediately after I came back and didn't die right away. Since you start with low energy after a death, my assumption was that there was a small forgiveness timer that gave you a chance to recover so that you didn't immediately end up back in Hell via performing one or two actions to get something that allowed you to recharge.