If this is just a storage container or topoff container you can do without for a few days I would just hit it with some bleach and scrub it then dry it out real good(maybe a day or so), fill it with ro/di then hit it with some chlorine remover like prime to make sure you got rid of it all. After you do that rinse it as many times as you think you need to then you're good to go. Short of all that I would probably just take it to the sink and scrub it all out w some tap then dry it with a towel being as it's just a 5gal.
All this being said if it's a white container that is getting light it's going to end up the same way in a couple weeks probably......get an opaque container w a lid if the discoloration/algae bothers you, problem solved.