New York State Fair
I can't speak to the NY State Fair specifically, but I have been with a group that has been trying to set up a kosher food stand at the NC State Fair for a few years. The policy there is that no new spots are available until an existing vendor chooses not to renew. Non-profit groups get priority (not a problem since we're a conglomeration of the local congregations, day school, and Federation). When we last applied we were told the wait list was roughly 8 years. People don't like giving up their spots, it seems.
So if the NY policy is similar, even if someone is trying to open a kosher food stand, Moshiach may get here first.
I go to the Great New York State Fair every year, although I won't exactly be able to answer your question, because I am really not sure.
For the most part, the fair is a great place to eat "bad" food. There are some great sausages vendors -- the Syracuse area is smitten with Gianelli and Basilio sausages.
That, in addition to corn on the cob, speedies, bbq and other greasy delights makes up the lions share of the food booths. (The New York state wine tent is also a big and fun attraction.)
But there are so many food vendors I wouldn't presume that one of them doesn't do kosher. Your best bet may be the international food court, where they have a great eggplant parmesan, perogies, and some middle eastern food like falafel and grape leaves that may well be kosher.