Actually what I meant was unsweetened peanut butter.

Because brands of sweetened PB can vary so much - and a lot of organized rides tend to get the very cheapest PB that's loaded with HFCS - if you serve sweetened PB, the participants won't know how much refined sugar they're getting. I understand that diabetics may want some refined sugar on a ride longer than they're used to, but not knowing how much is not a good thing.