We use plastic cups for holding my green power juices and the fresh vegetables and fruits can stain the inside of straws badly.  I purchased a “straw cleaner”, a tiny brush that can be pushed inside the straw for cleaning but have found it doesn’t reach the very center because it is too short.  Bill told me he found a way to get it cleaned and I want to share this helpful hint.  If you have the disposable straws that are thin and have a bendable portion, you can use it to slide into the larger straw.  The ridges of the bendable straw serve to scrub the inside of the straw!….or you could find a longer straw cleaner for purchase.