What do you feed a unicorn?

Okay, so the other day, I bought myself a unicorn and it hasn't been eating what I've been feeding it. I've bred horses before and because of their similar exterior, I automatically assumed that they both ate the same thing. I was terribly mistaken. It refuses to eat anything. I've offered it almost everything that's possibly consumable, but it won't budge. I'm starting to think it's a diva and only wants to eat a carrot grown in the Bahamas with Fiji water. (Or maybe it's anorexic. Do they have an institute for anorexic unicorns or is it only for humans?) And so started my pondering: what do you feed a unicorn? Do they feed off of happiness and rainbows or what? I don't want my unicorn to get malnutrition. Whether you have, had, or don't have a unicorn, please do not hesitate to respond. Any information on this will help tremendously.