Anything over a 300 is a stomach game for me. Rain, wind, heat, climbing haven't ruined rides, my stomach has. Stability is key. I used to think there was a magic answer for this, I'm less sure now. Eat something large and dependably digestable the night before. Eat a big, early, breakfast. Digest, get to the start early, snack, digest more.
I was cleaning up notes on my phone and found the list of things I'd consumed during my first 600km brevet. This includes only what I ate the morning of and during the ride, in no particular order. Sort of group by food type:
1 Banana
1 Orange
1 Pint strawberries
1 Bagel + 4oz of cream cheese
2 Waffles + syrup + butter
3 Eggs
8oz Chex mix
1 Bag of Lays (small)
1 Turkey/bacon/avocado sandwich (x-large)
2 Burger King chicken sandwiches
3 Rolled tacos w/ cheese
1/3rd of a meat pizza (x-large)
Lots of water
1 Iced tea (12oz)
1 Iced coffee (12oz)
2 Starbucks bottled sugary milky coffee drinks.
1 gallon of Gatorade
1 Grandma’s cookie
1 Brownie (large)
1 Ice cream sandwich
2 Clif bars
2 Fig bars (large)
2 Frosted donuts
Many peanut butter filled pretzel nuggets
Unequivocally, this was insufficient. By the end I was mostly on liquid calories, namely gatorade. I should've kept eating, but everything looked terrible. I wanted real food, but I wanted to be done even more than that.