PBP is a self supported brevet. However, all the control points along the route will be stocked with the usual supplies & spares for your bike. You can get warm food and snacks as well at the control There will typically also be bike mechanics available with necessary tools to help you with your mechanical issues. We recommend only carrying essentials that you would otherwise typically carry on a 400 BRM or 600 BRM. Also ensure you have spares that may be unique to your bike like a spare derailleur hanger or perhaps a spare 650B tyre. The bike shop at the controls will certainly have spare tubes and spare tyres but will likely have for the typical wheel size 700c. So don't go overboard with carrying 10 spare tubes or 30 energy bars in your saddle bag.
You will also find local French residents set up picnic tables along the route serving participants home baked cookies & cakes and even serve freshly brewed coffee. The atmosphere is very festive as you ride through the time-locked architecture of old French villages.