The high sugar thing refers to off-the-bike food. I think a lot of riders, myself included, will have simple sugars (soda, gel, etc) during a ride. It's when you're not active that such things become less useful. Remember that sugar is fuel and you burn it when you ride. Consuming a lot of it off the bike may not be great but on the bike is not so bad.

During a ride you should eat, as a basic rule, about 200 cal per hour, of simple stuff. For up to 2.5 hours you should have enough glucose stored in your body - it's when you go longer that you really get into the "wasted" zone. It occurs earlier if you're not eating a lot of carbs, so a protein-focused diet with no carbs will make you feel a lot weaker. Without carbs you have no easily used fuel. It's like making sure your car has oil and grease but to purposely leave the gas tank empty.

On longer rides I try and eat regularly from within the first hour. I'll eat whatever - Pop tarts, peanuts - to try and get some fat and longer term food in me. I usually avoid electrolyte drinks but after 3-4 hours I'll drink Gatorade/etc as it's easier to digest than orange juice and more fulfilling than a Coke.

As far as food before/after rides I'm not well versed. Generally speaking I ride better if I eat more carbs before an event (I feel pretty empty otherwise, even if I have a Coke or something just before/during the ride/race). After rides I crave salt and fluids, probably because I don't drink enough.

Yesterday, before an hour long event, I was up at 4:30 AM. At first opportunity I had an egg sandwich (9 AM?), coffee, pastry, then at about 11 AM another coffee, another pastry. Race was at 1. After the race (2 PM) someone asked me what I wanted as I was looking pretty wasted. I asked for, and got, 2 small Gatorades (they don't sell larger ones there), a Coke (skipped it, still have it, will save for another race), and a cookie. I downed both Gatorades pretty quickly, ate a cookie, and had a pastry. I wasn't hungry until about 8:30 PM (about an hour after I got home) when I was suddenly really hungry.

After the pro-1-2-3 race yesterday, 40 miles of brutal racing, a few of guys (top finishers of the race) finished, came in to get their prize money, saw some pastries I had put out, and wolfed down, between maybe the 6 of them, about two of the three 12x12x3 boxes of various food plus all but two pieces of pizza. They also had a bunch of fluids, water mainly. They all rode 20-30 miles to the race, at least one had done the 25 mile race with me (so the 40 mile race was their second race) and were preparing to ride back home. They're also all super skinny and lean. Ride enough and on ride days you can eat almost anything you want. It's usually better to eat something than to try and ride while you're light headed from lack of carbs.