In a brevet you can self support at the local 7-11 and such. You can't receive support from people though. You can't have a personal support vehicle and you can't have a friend deliver mechanical aid, food and so forth. I've read that in the PBP local merchants will give food to riders. Since it's offerred unexpectedly, I guess that's all right.

So, it really depends on what the route provides. I use this snazzy bag for the brevets I've done:

Moots Tailgator