Like Randy says,some vend at the contest.
Some may have restaurants,and they vacpac,chill and take back to work.
If it is a cook close to home,friends/neighbors may come out to eat and carry away leftovers.
Some teams may have sponsers that come by,and they have even cooked extra for them.
Someplaces may have a peoples' choice contest,where spectators can pay to come by your booths,sample your leftovers,and give you a score.
A local team may have a charity and they will accept properly packaged leftovers and deliver it.
Ronald McDonalds,local food bank,etc.
Some throw it out.
Hope this helps a little.