I use my vacuum flask to bring my lunch to work. I've been doing this almost every day for half an year or so. Now there are some sediments or stains in the bottom of the flask although I wash the flask almost always immediately after it's emptied.
How can I get rid of the stain and smell inside the flask? I even used steel wool on a stick but could't make it clean 100% and I don't want to scratch it too much inside. Because I use it for food I am not sure if bleach is a good choice to go for.
I have original Thermos made of stainless steel interior and exterior. Something like that one http://www.thermos.com/products/vacuum-insulated-10-oz-food-jar.aspx
Note that I am located in Austaralia so no cleaning products are available to me.