Personal experience.
Submitted claim, called for audit.
Submitted receipts and sandwich wrappers (bit reesty, but they asked). Not seen since.
The audit process appears to be neither random nor 5% in the RAF. If you submit a claim for anything which doesn't PRECISELY fit the expectations of the compooter, expect to be audited.
Kitbag makes a fair point though, except that I am not sure the average fast food place is any better or worse than what's served in most RAF feeders!
STH