Do they have Vegan Food?

Yes

There are some vegeterian options available for some restaurants as per guide map, listed here: Plaza Café, Grande Oak Picnic Pavilion E. and W., Katy's Kettle, Soda Springs, Soda Shack, Ace of Clubs, Johnny Rockets, Food Etc., Frozen Delights, Goliath Goodies, Wascal's and Snack Shack.

Not really. Go to the restaurants that are outside of the park for vegan. Six flags food is just theme park oriented, not a healthy choice

They have a sushi place next you Goliath they have california rolls, salads and fries I haven't really seen much else