It always made me a bit upset when tea left rings and stains on my mugs. I tried using different brands of dishwashing soap.
I've heard that some people use bleach to wash their mugs but I don't feel comfortable using it. One day I came across this wonderful idea. It is safe, super easy and works wonder.
Mix baking soda and a little bit of water (just enough to make a paste-like consistency) in your mug and scrub all the stains away with your finger.
Voila! Your mugs will be clean like new.