If you're not feeling sick during the race, then maybe it's more about that coke, water, candy bar, and bagel with cream cheese that you're scarfing right afterwards. Grab a sport drink and spin your legs out a bit after the race. Stay bland with the food. I like pop tarts right after races or hard workouts. Or a PB & honey sandwich on white toast.
When I say I scarf on McDs, it's a couple of hours after the actual race, on the ride home.