It really depends on how long your labour is and also how long before going into labour you ate.
My waters broke but contractions never started, so I was induced, Therefore I made sure I ate breakfast and lunch before going in.
When labour started contractions were 3 minutes apart and continued that way, and getting stronger the whole time, so food was the last thing on my mind. I did however suck on ice cubes like there was no tomorrow. That way I didn't get dehydrated.