A good 24 hours at least is best, although with plastics it can damage them, and also some metal surfaces are painted nowadays, and they also don't like being in bleach. For items unsuitable for bleach I would scrub well with a good antibacterial hard surface cleaner and then rinse well. Repeat process if any stubborn stains remain. Urine stains and limescale deposits can be eased away with the use of a clear vinegar (not malt!) solution (neat or diluted depending on the severity of the buildup).
After this pop them in a baby sterliser solution. This is designed for use with plastic feeding bottles and teats etc so safe for your hamsters and man made materials. I sometimes soak up to a week in baby sterilising solution. When recycling between hamsters wooden items should always be disposed off even if only bought the previous week, you just cannot sterlise them sufficiently, and water bottles too I personally think. For the sake of a few pence/cents a new water bottle is not much to ask surely?
Interested to hear if anyone else uses anything else? I have heard of denture tablets being used