Keep your body fueled. While most century rides offer some type of refreshments at rest stops, there is no guarantee that the rest stop will have what you need when you need it. For this reason, I carry enough Energy Gels to ensure I can stay fueled. I also set an alarm on my bicycle computer to remind me to consume some carbohydrates to fuel my legs. Normally I prefer whole foods like apples, oranges and bananas if they are offered at rest stops. However, I do use processed carbohydrates on centuries ride if I need them.