As with most items of equipment a little regular care and attention will pay dividends in terms of longevity, general hygiene, and overall biosecurity.
Regular washing with warm soapy water will remove most ordinary day to day dirt and the inevitable bird droppings. Try not to use harsh household or industrial chemical products. If you are using a disinfectant be sure to use the correct dilution rate as specified by the manufacturer. There is no sense or advantage in using too concentrated mixture which might even damage the plastic material.
Take the feeder or drinker apart and tackle each individual component, use a soft brush on stubborn areas but be careful not to scratch the surface as this will be a point where micro-organisms will prefer to breed. If you have used a disinfectant mix it is best to rinse off with clean water. A pressure washer may be used but not on the maximum setting, mains pressure or a little above is all that is necessary in most instances. Always allow to dry before re-filling and putting back into use.
When not being used or at the end of the rearing season follow the above procedure then store in clean dry place, well ventilated and away from direct sunlight, ready to be used when required. Well before they are required check all is well ready to put back into use.
Be aware that vermin may still take a fancy to drinkers & feeders in storage even if there is no obvious feed material present.