Oh yuck! Make sure you don’t leave your KeepCup at your desk overnight without at least giving it a rinse with hot water! For any lingering smells or tastes we recommend mixing some bicarbonate of soda with some water or lemon juice to make a paste, then gently wiping the paste around the inside of your cup and leaving it overnight. You could also try ‘perfuming’ the cup by leaving coffee beans sealed in your KeepCup overnight.
Please try those options and let us know if they’re not successful in getting rid of the smell/taste and we’ll look for an alternative for you.