When my DP was in hospital for a week with our DS in January, I would visit with a hot flask of covent garden tomato soup for her as the hosp was s**t! After it was used I would thoroughly wash the flask out every night. We haven't used it since then but yesterday I decided to make a flask of tea, but ended up having to throw it away cos all I could smell was the soup. Any suggestions on how to get rid of the pong?