I've been writing/RPing a storyline with Roulette here in which she has an Ethereal compatriot/partner in crime. I'm having a lot of fun with it, Goblins and Ethereals are delightful schemers. Course there's also a lot of holes in the lore for Ethereals. I can afford to be vague about K'aresh details and culture, things like that, as it suits the character. But eating and sleeping are kind of a big deal and really handy to know.
I've gotten all I can out of Wowpedia, which basically says "Maybe."
Ethereals appear to need to eat and drink, with their vendors selling specialty bread and drinks not found on vendors of other races. Based on the foods Eyonix sells and their interest in gems, it could be thought they eat them and precious metals. Alternatively, Ethereals may not eat at all and sell food only for the sake of the more corporeal beings with whom they trade and interact. It is not known if they sleep, for even if they have inns, it could be stated that they do only for business purposes with other races; however it is more likely that they do not need rest, since their encampments lack true shelter or any form of relief.
If Ethereals ever became playable, I would totally roll this character and I would assume that sleep and eat emotes would be included. But that's a really big if and I'm not sure I should take that leap or not. What can I say, I'm a stickler! Consuming gems certainly sounds interesting though I have no idea how that would work given they have no mouths or teeth or stomachs. :P
So... yeah, I'm a bit stumped. Any thoughts, input, advice, are welcome!