My husband has a tendency to empty bottles and put them in the dark cabinet while they are still wet. Needless to say, they get icky.

Since I've started letting them dry before putting them away, there isn't an ounce of mold, or algae, or anything. Funny how that works.

Also, Rubbermaid makes a brush that is technically made for cleaning sinks. Its a long handled brush that has a bit of an angle at the end. Works great for getting into the edges of the bottle.