If I read correctly, maximum strength NoDoz has 200 mg of caffeine. A serving of coke or coffee has about a quarter of that. I think I'd climb the walls on 200 mg. I think I'd just stick to gels with caffeine or some flat coke. I'm not generally a soda drinker myself, but sometimes Coke tastes really good during or after a ride.
I wouldn't suggest dosing up on caffeine the day before your race though as it might interfere with getting a good night's sleep. If I drink any caffeine after 10 or so in the morning, I'll feel it later that night. I'll fall asleep okay, but I'll wake up in the middle of the night with a racing heartrate.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher