This is what works for me on a century or longer ride ...
Eat about 500 calories for breakfast ... eat whatever works for you.
Aim to eat about 200 calories per hour while riding. I say "aim" because I don't usually actually hit that. I've found some granola bars that are about 180 calories, or cookies, or gummy candies or whatever. I have them in my handlebar bag and bento bag and just eat while I ride or when we stop to use the toilet or whenever.
If there is the time and opportunity to sit down and have a meal mid-ride, I'll do that.
Tuck a couple gels into your handlebar bag just in case. Sometimes late in a ride, my stomach will decide it doesn't want solid food and that's where those gels can come in handy.
Drink approx. one 750 ml bottle of water every 1 to 1.5 hours.
Consume electrolytes in food or in capsule-form.