I think @wilcolandzaat removes the snap ring and pulls out the guts to clean his Sanke kegs. Commercial breweries have a very expensive machine that sprays caustic acid in them. If you Google it there are home brewers that have made some stuff to clean them.
Back a long time ago I used a Hoff Stevens type keg for homebrew. They actually still had a bung. I pried them out so I could spray around a little inside and after filling hammered in a new bung. It worked but I still wondered if some gunk got left behind.
Any Sanke kegs I got became brew kettles after that.