Eating is pretty important. You'll find that when you don't eat enough it's almost like you're hitting a wall. Everything gets miserable, and your strength disappears. You have to remember to eat more when you're cycling to work . . . I've had that 'oh shit' moment a couple times where my hands were shaking and I was getting dizzy coming home. Keep some food at your desk at work (raisins, craisins, dates, cereal, etc.) and grab a couple handfuls before you head home. I tend to get much hungrier on the bike when it's cold/windy than when it's hot.
This is pretty good advise and I wouldn't dispute it for most riders. However, I'll
offer myself as a counter-example of an alternative approach.
About 4 years ago I switched to a ketogenic diet (mostly healthy fats, some protein,
and very few carbs). After a few days of getting my body adapted to this diet, I rode
five 200K rides with friends in a fasted state -- I ate nothing and drank only water
and black coffee. I did this 5 times at a moderate pace, probably no more than
60-70% threshold. My friends were aware that I was doing this and monitored my
well-being during the rides.
From keto at 3 meals per day, I gradually switched to 2, then 1 (OMAD). I did all
of my recent 100K training rides in a fasted state, and even managed to jump onto
some fast pelotons. On my recent Seattle-Vancouver-Seattle ride mentioned
downthread, I maintained OMAD, though I ate more carbs than usual due to
dining out with friends.
None of this is to suggest you shouldn't eat frequently if you're on a normal
diet, but I thought I'd mention my experience as an alternative.
When it's very hot I have trouble eating anything on the bike (it's one of the few times I feel kinda nauseous), so on long rides will always prepare sugary gatorade type drinks to sip (although after four hours of sipping as they warm up, drinking them gets a lot less fun). Gatorade type drinks are also good because I find that I sweat a lot - my jersey is crusty with salt when removed - and therefore drink a ton of liquid in the heat . . . if I'm just drinking water I get pretty bad muscle cramping. If I do the sports drink thing, no muscle cramping. You can make ghetto Gatorade by mixing some sugar, lime or lemon juice, and a couple pinches of table salt in your bottle . . . or you can just buy the powder which is also pretty cheap.
When I was still eating (i.e. non-fasted state) on the longer rides,
my preference was to keep hydration and nutrition separate. When it's
very hot, it's sometimes difficult to consume beverages other than plain
water. With a Camelbak, I could pack a lot of ice and keep the water
cool for many hours. I would also consume electrolyte capsules in hot
weather to avoid hyponatremia, as I once had a friend go into a coma due
to this on a particularly difficult ride. She recovered after being airflighted
off a mountain.
Finally, I'm not a fan of sugary drinks and have always avoided simple
sugars during training and events:
https://www.hammernutrition.com/knowledge/getting-started/2-caloric-intake/https://www.hammernutrition.com/knowledge/endurance-news/athletes-teeth-in-trouble/Also, since I've cut sugar out of my diet a few years ago, my dental checkups
have been much improved. :-)