Well the amount of replies is staggering but a bit bewildering as so much info to digest!!!!
What about eating the night before? Any advantages to eating certain foods or at a certain time????
Just eat normally. Have porridge for breakfast, or whatever you would normally have. Take some flapjack and jelly babies. And cash for lunch and cake stops. And a couple of bottles of water / squash on the bike
You can stop, rest and eat when and where you feel the need
The thing to plan is how you get back if the untoward happens bonk, mechanical, take a tumble)
Don't overthink it, you're not riding the TdF on the moon.