Research shows that a mix of sugars and carbs can enhance digestion, rapid and long term metabolism for fuel.

If you're drinking plain water, try adding some electrolytes. Plain water tends to sit in my stomach and makes me feel bloated. I find DripDrop suits my digestion best. I dilute it more than recommended and it still works great. But don't overdo it with electrolytes, especially salt tablets. I've seen runners, cyclists and fellow active duty military on long marches with full packs suffer worse and even vomit from salt tablets. DripDrop has data on their website explaining why a mix of sugar is essential to aiding rapid digestion.

Most energy snacks contain the same ingredients: various sugars, including sucrose, glucose, dextrose; maltodextrin, which is generally easy to digest without problems for most folks. If we're expending enough energy that sugar gets burned up pretty quickly.

Some substitute sugar alcohols. While those can help avoid insulin and blood sugar spikes, maltitol and other sugar alcohols can cause digestion problems for some people. They make me gassy. If you're in a group ride and trying to hold it in to be polite, it's gonna get miserable pretty quickly. Drop to the back and let 'er rip. Or don't eat snacks with sugar alcohols.

There are disagreements over the value of protein for most workouts. And some folks can tolerate whey protein but not soy or legume based proteins. Takes some experimenting to find what suits your digestion. I cannot digest legume or vegan proteins, so I use only whey for workouts, and my diet is primarily carnivorous, although I'm not religious about it. I'll add veggies for flavor and variety. But no beans.