washer reservoir and overflow tanks

What works good to clean the plastic containers? My Caprice is the first vehicle that I've had with these parts. I usually drive 40s and 50s cars and trucks. I've heard some things that work, but don't remember what. Bleach, vinegar ? What have you guys and gals used? Thanks.

I would start with a good detergent. If that does not work, maybe the vinegar. I would be hesitant to use bleach, because it just makes the dirt look like it is not dirt. A bottle brush to agitate the mix might help. Be careful if you have an LT1 car, because the level sensor is in the overflow tank, and could be damaged by some cleaners. The washer tank sensors can be removed.

I would think some CLR. Be sure that everything is fully flushed out with plenty of clean water!

Speaking specifically about the coolant bottle: It depends on what's in there. I've tried a few different things- vinegar, CLR, probably some others without much luck. How bad is it? The one I got with the car was totally caked with brown sludge. I ended up just replacing it for one that had far less sludge. I cut the original one open to see what's going on inside.

The chambers are connected by very small passages, so even if you dislodge big chunks they may be nearly impossible to get them out. I spent a couple of hours with the hose filling and shaking and dumping until I got a lot (but not all) of the crud out.