Anything less than about a 2 hour ride, you probably don't need to eat anything special beforehand or during the ride. Unless you're currently running an extreme low-carb diet.
Anything over 2 hours, and you need to think about how you're going to make your body's glycogen stores last longer. This is almost always in the form of eating some carbs along the way. If you want to keep your activity level much lower, you can keep your body in a more fat-burning activity level, which will keep you going longer - at a much slower pace.