Some people collect shot glasses of places they've travelled. I like to collect bidons.
I love having bidons that have some sort of memory attached to them, or that look great on a specific bike. Older ones sit in a bag deep in my bike stuff trunk. My wife wishes I'd get rid of them along with my old kit, so they're very out of the way.
"Bidon" etymology: From Middle French bidon (“small portable container, sealed and made of wood or metal”), from Old Norse *bida, *biða (“container, vessel”), from Proto-Germanic *bidōn, *bidjan (“tub, vessel, vat”), from Proto-Indo-European *bʰidʰ- (“pot, bucket, barrel”), from *bʰeydʰ- (“to weave, bind”).