There isn't a dedicated 'gut wagon', but on bigger incidents we usually try to round up some sandwiches or something.
Normal things include:
Gatorade, tea, coffee, hotdogs, sandwiches, all bran bars, and occasioanally timmies by times.
Personally favourites I've had:
Cold hotdog, with ketchup, and a soggy napkin stuck on the bun. Didn't even notice the napkin.
Tea, stirred with a screw driver, in the absence of stir sticks.