Best way to clean inside of Better Bottle?

I've used a Better Bottle for my last few batches, and haven't had too much trouble cleaning it out since I have a spray wand but this last batch must've left some extra stubborn kraussen. Does anyone have any good tips for removing this? I soaked it overnight in water, but that didn't help.

Are there any products you use for soaking to loosen it up? I'm hesitant to use anything to scrape the crud away since I don't want to scrape the carboy itself. Thanks for the help!

People on here swear by oxyclean, I've never used it yet, but plan to for removing labels on bottles. A bleach soak should work as well but I don't know what material the better bottle container is? Check with others first before using any harsh chemicals, but oxyclean should be safe.

I use oxyclean and hot water for everything...I use a couple huge scoops/5 gallons, and never have had any gunk stick anywhere... I usually let it soak overnight...

Hot tap water and PBW works great. Let it soak for a few days.

TO save time, I usually just put a wet washcloth in a better bottle and shake like hell for a while.