Denture cleaner. I use denture cleaner to clean out my water bottles. I have a SIGG one that is aluminum, but lined. The denture cleaner gets it real clean inside without wearing down the liner.
I have a new klean kanteen which is stainless steel. It's more dishwasher friendly, but I still use the denture cleaner cause it's easy. You just plop in a tab & fill with lukewarm water. I bought the mint tabs, so they leave the bottle minty fresh!
A friend may well be reckoned the masterpiece of nature. -Ralph Waldo Emerson