What I do is take a plastic shoe box container, put little holes in it, put warm water in it, enough for your snake just have about a half, maybe a little bit more but not much, of him is covered. I've heard putting a wash cloth in the container will help as well.
But, it SHOULD be okay to do this in the sink, but im not so sure. This thread here should help
http://ball-pythons.net/forums/showt...hed-No-problem