Everest is technically not supported, but having people/family/friends/whatever hand you bottles is support.
They do have food and water (HEED,etc) support- there's feed stations where they'll give you bottle handups or you can stop and grab some food.
There's enough that you can do it without personal support if you stop by your car when you pass it during the race.
There is neutral support (for wheels etc) but its availabilty is sketchy- the start times are spread over an hour and the riders end up spread out
by more than that on the course.