i recently stuck mine in the bath and showered them down....
otherwise, towards the end of a ride i find a nice long puddle (at least 2inches deep) and gently roll through it.
20 years ago, before environmental issues weighed us down too much and I lived in a student house owned by the uni where all bills were paid, we used to clean the dishes by placing them in the large showers, cover in fairy liquid, turning the showers on and then pissing off down the pub. 3 hours later and the dishes were spotless. Bikes were cleaned using a similar method but in the sports hall or halls of residence showers