I am still experimenting with what to eat the day of a meet. I have a senstive stomach as well as no appetite before or during meets and if i do not constantly eat i get very light headed throughout the day. I found the best thing to do is to eat oatmeal for breakfast. It starts the day off with a decent amount of calories as well as carbs and protein and since it has a low glycemic index it will not raise your blood sugar level and cause you to crash and feel tired later on. Then an hour before and after each race i drink an "ensure", or a "boost". It seems to satisfy my caloric needs and doesnt leave me feeling hungry or lightheaded. They are only 8 ounces, easily to down quickly, taste ok, and cause me no GI stress. Just make sure you have a something solid in you stomach as well so you are not running ot the bathrom every 5 minutes.
What you want to stay away from are foods with a high glycemic index
BAGELS, COOKIES, CANDY, DOUGHNUTS especially! Eat these and an hour later you'll be sleeping in a corner.