Hamburgers, meat sandwiches, fries and coke are out. In your water bottle you want to be drinking a high energy replacement drink, a re hydration formula. These are digested at an even rate. Coke and high sugar drinks are quickly absorbed and you get a sugar high followed by a low. For food try to stay with simple things like bread, soup works very well and no fat.
Pretzels are great.
On the trail, a Power Bar or two will provide enough energy to get you through the day with out filling up on hard to digest foods. Ibuprofen and good old aspirin as recommended, during and after the race is quit useful. An antacid such as Tums, will settle the stomach and provides a good source of Calcium. After the race, the good news is you should eat enough to replace the lost carbohydrates as soon as possible. This will speed your recovery.