Probably just quits and comes back to (a probably new) employer in a few months or is self-employed. I took 9 months off of work, I wouldn't call it a sabbatical but you could phrase it that way I suppose. Funemployment.
That does sound nice, but a sabbatical usually means you're at least partially paid and you continue your old job when you come back. Also, I don't think I know anyone just out of college who could afford to do that.