To clean the inside of the stainless steel canteen, you can use a handful of steel shot(from shotgun shells) and a dollop(that's right) of Javex powder or Bon Ami or any other abrasive bathroom cleanser. Just enough water goes in to lube everything and shake in a rotational fashion to clean. Mucho washing to get the cleanser out, and repeat until shiney and new looking. Use lots of shot and it works better.