Considering this is your first post, welcome to Smash World Forums. I agree that this isn't something that is widely talked about and what you eat may make a difference. I don't want to say with certainty that it will because that requires evidence on my part, and I'm not willing to make statements that aren't scientifically supported. I think what we can all agree on is that breakfast is the most important meal of the day because your body has been fasting for the past 7 or 8 hours of your rest. Hence a breakfast.
Here's a list of things that can help with your mind. Aside from food, you want to make sure you get plenty of rest. 7 hours is really all you need, but 8 hours is fine, too. Anything more or less is not good for your health. You might also want to stand every now and then so that you can get your blood flowing. Blood needs to reach your brain, after all. You could also try meditating. It's not difficult. You can take 10 minutes of closing your eyes and just sitting upright in a chair if you feel awkward putting yourself in a lotus position.