A light nylon line to hang washing on, plus a couple of pegs and 2 cheap plastic hangers which really help to dry shorts and jerseys.
Earplugs & an eyeshade (I’ve found wax are the most effective! E.g. Quies)
A USB charger: Lots to charge overnight – Phone, Garmin, lights and so on. (Pack light with a travel multi-USB port charger, e.g. Syncwire)
Flip flops for the “flip fop” bag. The last thing to go into the van and first off at lunch & the end of day – great to wear when off the bike!
Microfibre travel towel – towels won’t be provided at the hostels