I made chocolate/oat/date balls for mine. I read somewhere how many calories I could digest per hour and sized them appropriately so that I could eat one every 15 minutes. I also did a sweat test to figure how much salt I would need and added that to the balls. I started eating a couple of hours in and just took them like clockwork. I also drank a ridiculous amount of water (maybe 10 L) and had to stop to pee many times. I didn't eat anything provided, but I did drink gatorade at every aid station. If I was racing, carrying and drinking that much water would have slowed me down. Since I was just trying to finish, it worked out okay, especially since it was an unusually hot day for October and around 20% DNF'd.