When I was competing, I experimented with a lot of different bars and snacks to find what would work the best to give me the energy I needed on court to finish a match. As I suffer from tummy troubles, I had to find something I could eat that wouldn't upset my stomach if I played right after eating it, or if I ate it during a match. Here's what I found...
*Disclaimer: Please check labels carefully to make sure you are not allergic to any ingredients!
Check the Nutrition Facts label and look for the following 5 items:
1) Carbs: You want high complex carbs for sustained energy.
2) Sugar: You want a low sugar count. If the sugar & carb counts are the same, that means the carbs are all sugar and you will experience a "Sugar Crash." That's bad.
A good ratio is 2/3 carbs, 1/3 sugar.
3) Sodium: High sodium is good to replenish what you sweat out.
4) Potassium: The higher the better to ward off cramping.
5) Protein: In between & during matches you want a low protein count as it takes much longer to digest than carbs. Protein up AFTER you play!
I've had the best luck with Luna bars and belVita bars. They both come in many flavors to please the most discerning of palates. You'll find the Luna bars in the organic section, and the belVitas in the cookie aisle of most grocery stores. Again, please read the labels for any possible allergens.