Quoting LinzKae:" I was thinking toast but wasn't sure if I would have the energy I need during labor."
That food energy will run out anyway and if you eat too much it will make it way harder than not having eaten enough because you will feel sick while you're in the worst pain of your life as opposed to just being in the worst pain of your life.
I was in labor for 17 hours, I have heard of people getting exhausted but I personally thought it was not nearly as tiring as I had anticipated. I didn't feel that tired and I went off of 45 minutes of sleep.
You know your body best though, I know that having food in my system makes my pain a lot worse for my period, so that's why if I knew I was going into labor I wouldn't eat a lot because I know how my body reacts to it. Yours might be the total opposite!