I think you should look at the science behind fasted cardio as it has been shown as a good way to burn fat. My experience has been under 20 miles I just go and am fine.
20-50 you will feel better if you eat carbs the night before. For me this is a pint of low alcohol beer (4.75% lager) and some pasta. During the ride, just eat some carbs... it is not complicated but bananas and fig bars are good choices. Eat small and often.
For me drinking (water) is really key. A lot of water before I go. A water bottle per hour along the road. Learn to drink on the bike and you will be happy!