Searching around and couldn't find a good thread on this question yet. 

My question is simple: What all counts as "sleep" in relation to the benefits of Aspect of the Moon?

Obviously there is the main explanation which I understand meaning I do not need to fall asleep to rest and can't be forced to sleep magically (such as a sleep spell).

What i'm looking to detail is what else counts as sleep? Can I pass out from being drunk? Can a squeamish character faint?

I assume hitting 0 HP obviously still makes my character unconscious.   What i'm unsure of is the gray area items between 0HP unconcious and a nightly rest.  What is affected by Aspect of the Moon and what is not?

Drinking yourself unconscious is something that doesn't have rules in this edition of D&D as far as I know, but it would be a poison effect under D&D rules.  Any effect that says it renders you unconscious rather than put you to sleep would still work.

Poison effect?  Someone can't hold their liquor, no dwarves in this thread.

As you stated, you do not gain immunity to falling unconscious - just falling asleep. The area in between can be a bit gray, but I think its pretty easy to distinguish if you stop and think about it.

Since the game rules don't codify the word "sleep", we use the generally understood meaning in the English language. That can be your simple test. If a person would reasonably describe a particular event as 'falling asleep', the warlock would be immune to it. Otherwise, it would probably be considered 'falling unconscious' and the character would not be immune. Some examples:

• "He is so squeamish about blood that whenever he sees it, he <falls asleep>. Doesn't work
• She took some pills before bed and <fell asleep> when she hit the pillow. Works
• He had a few beers with dinner and ended up <falling asleep> in the middle of the movie. Yea, that probably works
• He hit his head so hard that he <fell asleep> for a few minutes. That doesn't really work
• He took a dozen shots, vomited, then suddenly <fell asleep> This is probably a bit gray, but I'd argue that its too much of a stretch and most people would say that he "blacked out", or fell unconscious.

In the manners of being drunk - you usually get to a point where your brain makes you unconcious due to intoxication.

If you have aspect of the moon, you would most likely wake up rather soon after going unconcious and have a huge hangover for way more hours then those that can just sleep it off.
I do not recommend drinking and Mooning.

As I have recently found out, per the rules, a dragons breath isn't magical. Some dragons, like the brass dragon, have sleeping gas effect as one of their breath weapon options. Since this is technically not a magical sleep effect, it  is not covered by the immunity to magical sleep.

Edit: had to fix an auto (in)corrected word to the correct word

Fainting because of squeamishness and Passing out from being drunk arbitrarily fall under the umbrella of "sleeping" but are more akin to being incapacitated rather than unconscious. The short and sweet is that you don't need to sleep, but you still can if you so choose.

The dragon breath weapon would not work (at least in a game I run), because you cannot be forced to sleep by any means, according to the verbatim in the invocation's text, which includes both magical and non-magical. I suspect that unless there's something which specifically iterates overcoming resistances or immunity to this effect, for the sake of forcing a character into unconsciousness, it will remain that way as per RAW.

StylesStriker I assume aspect of the moon is worded exactly like the Elf and warforged trait which only mentions that they cannot be magically put to sleep.

While each DM can run their games how they want, but the RAW of it, a Brass Dragon who uses their sleeping gas is not magical and therefore can put an elf or warforged to sleep because they are not immune to bring out to sleep through non magical ways (poisons and other affects).

Nope, Aspect of the Moon says "you can't be put to sleep by any means" unlike the elf and warforged entries that just say that magic can't put you to sleep.

What gives the aspect of the moon?

Its an Invocation that Warlocks can choose.

It is an invocation you choose under the prerequisite Pact of the Tome, which you can choose as soon as you meet the prerequisite. It's text reads as follows;

Aspect of the Moon

Prerequisite: Pact of the Tome feature

"You no longer need to sleep and can’t be forced to sleep by any means. To gain the benefits of a long rest, you can spend all 8 hours doing light activity, such as reading your Book of Shadows and keeping watch."

Suffice it to say it is an extremely useful invocation, or ability to have in general for yourself and for a group. I'm sure there are DMs out there with whom players work out various details to count what is or is not "sleep", but semantics aside its general use goes towards being the one in charge of keeping watch over camp while everyone else get s along rest, lol.

Quote from 6thLyranGuard >>

Nope, Aspect of the Moon says "you can't be put to sleep by any means" unlike the elf and warforged entries that just say that magic can't put you to sleep.

 no, Aspect of the Moon says you can't be FORCED to sleep, so spells like Catnap etc where you have to be willing, CAN still put you to sleep i believe

Silly question, but would Aspect of the Moon protect people from exhaustion? As exhaustion most relevant cure for exhaustion is sleep?

Quote from roselanih >>

Silly question, but would Aspect of the Moon protect people from exhaustion? As exhaustion most relevant cure for exhaustion is sleep?

 No.  If it protected you from exhaustion, it would say so in the description.