If you have a dishwasher you can turn them inside out and use a clothespin to pin them to the top rack of your dishwasher, that works pretty well. Otherwise, make sure you use really hot, soapy water. It takes pretty hot water to break down the grease from BC icing. Especially important if you use the same bags for Royal and BC! HTH
I have rinsed them out with hot soapy water, then tossed them into the washing machine with a load of towels. I make sure they are turned inside-out. I then run the machine w/ hot water, my regular detergent and a cup of bleach. I don't do this everytime, but about every other cake or so.
I use hot hot water and soap. My instructer seemed to think the dishwasher would make them fall apart? 
I have separate ones for royal icing , i dont want to take any chances with that stuff. 
I was just readin this post and saw what DianaMarieMTV wrote about using the same bag for Royal and BC Icing.
I THINK SHE HAS FINALLY SOLVED MY ROYAL ICING MYSTERY!!!! THANK YOU, THANK YOU, THANK YOU!!!!!!! 
The grease from the BC gets onto the Royal icing while it's in the bag. I can't belive I never even thought of that! That's the reason my roses always turned out runny and never would do right!
Y'all are some kinda smart on here!!!!! Thank you so so so so MUCH DianaMarieMTV!!!!!!! 
Connie
Laurieloo
I got really, really, really tired of trying to clean them and getting off all the grease, tried the dishwasher but the water doesn't get hot enough for me so I went to disposables now. I know, I know, expensive habit 
.....but what it saves me in clean-up time is well worth the few cents more I have paid for each cake. Besides, since doing cakes, I have gotten dish-pan hands!!!!! My finger nails are soft and awful looking also. Don't get me wrong, cuz I am not vain, geez even put my fingers in photo developer when in the dark room, but I really, really, really hate doing dishes and them grrrrrrr bags. 
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