I found an article on Active.com that gave the 5 best foods to eat before race. I personally can't handle eating too much, I might have a banana and an energy bar, then fuel throughout the race, although I migh try one of the meal replacement shakes as well.
Bagel
A bagel makes an excellent pre-race breakfast food, not only because it's rich in carbohydrate, bland and easily-digested, but also because it's something many runners eat for breakfast routinely, hence familiar. Eat it dry or top it with something low in fat such as a light smearing of reduced fat cream cheese. (or I think add some jam)
Banana
Bananas are almost all carbohydrate. A large banana contains more than 30 grams of carbohydrate, just one gram of protein and no fat whatsoever. Bananas are also high in potassium (400 mg), which is lost in sweat during running. Their softness and light taste make them easy to consume even with pre-race nerves, and their natural "wrapper" makes them handy for eating on the road.
Energy Bar
Energy bars such as PowerBar and ClifBar are made to be eaten before exercise. Most are very high in carbohydrates and low in fiber, fat and protein. The better bars also contain useful amounts of sodium, potassium and the antioxidant vitamins C and E.
There's a huge variety of energy bars on the market--some are better than others. Choose one that's close to the PowerBar formula. Avoid the high-protein, low-carb bars that have become popular in recent years. The advantage of the wide selection of bars on the market is that it's easy to find one you like and can eat without unpleasantness before a race. Pay attention to texture too. Some bars are very chewy, and for some runners eating chewy foods tends to exacerbate the stomach churning that's associated with pre-race nervousness.
Meal Replacement Shake
Drink one or two meal replacement shakes the race. Brands such as Boost and Ensure have a nearly perfect nutrition profile, they take care of energy and hydration needs, they're super-convenient, and nothing is easier to consume before a race--even if you're extremely anxious. And they taste good.
Ensure, for example, delivers a whopping 250 calories of energy in a little eight-ounce can, including 40 grams of carbohydrate. The one downside to these beverages is their efficiency. By providing so much nutrition in such little volume, they are not as filling as solid foods and can actually leave you feeling hungry in the middle of a marathon if you rely on them solely.
In the same general category as meal replacement shakes are performance recovery drinks including Endurox R4 and Ultragen. They are normally used immediately after exercise, but they can also be used for the purpose of pre-race fueling. They are sold as powders that you mix with water. Because these drinks are slightly more diluted than meal replacement drinks, they do an even better job of hydrating and fueling simultaneously.
Oatmeal
Like bananas, oatmeal is almost pure carbohydrate, plus soft and light in taste. It is also the most filling food among the five best pre-race foods, which is good for those wanting something substantial in their belly before they head out to burn a few thousand calories. Some runners also prefer to eat a real breakfast food for breakfast, and oatmeal certainly provides that.
Oatmeal requires preparation that can be more challenging on the road than at home. If your hotel room has a microwave oven, you're all set as long as you've brought some kind of bowl with you. If there's no microwave oven, you can use the coffee maker to heat water.
Water is usually the most boring beverage out there but I drink water for most every meal. Most times I'll be the first to tell you I want to splurge on Sprite, Rootbeer, or juice, but the benefits of water are real, especially for athletes like us. There is no room to skimp on hydration.
All functions within the body require the presence of water. A well hydrated body enables these functions to occur quickly and efficiently. All chemical processes involve energy metabolism and drinking plenty of water will make us feel more energetic and boost our metabolic rate. 
Fruits and vegetables - besides being good sources of vitamins, minerals and fiber - fruits and vegetables contain lots of water. For example, oranges are 87 percent water, and cucumbers are 95 percent water. Milk, juice and other beverages also have large amounts of water. Conversely, dried fruits, nuts, grain products and baked goods generally contain less water.
