Depending on how much cake is built up inside, you can probably get away with a Salt and Alcohol treatment, and then using some pipe cleaners dipped in high proof alcohol inside the stem. If the stems taste bad they may be oxidized and a soak in OxiClean and a good once over with a Mr Clean magic eraser should do the trick.
http://www.youtube.com/watch?v=-HyyB9ssGH8