Not eating is TERRIBLE advice. You are actually less likely to barf if you have a little food in your stomach. Trust me, I've been teaching people to fly military aircraft for over 6 years now and having something to eat for breakfast is a much better way to fend off airsickness.
I recommend having some protein, because it digests slower and gives your digestive tract something to work with instead of just having stomach acid sloshing around in there. A "perfect" breakfast is something like an egg mcmuffin (make your own so it's not as greasy) and a bananna. Why the bananna? Because they taste better coming back up than egg mcmuffin

Having an all-carb breakfast will screw with you, so don't just have cereal or a sugary breakfast bar or pop-tart. You'll end up with a sugar/insulin spike/crash, which can add to inflight feelings of distress, which leads to barfing. Get some protein in there, make it a smallish but complete/balanced meal and you'll do better.