Warm water, dish soap, and light brush or cloth. Hard scrubbing may remove paint or insignias so refrain from that. The stickiness, from what discussions I have read, is thought to be caused by natural breakdown of the plastic. It will return with time as all plastic breaksdown eventually. The frosting is the same and some have said it returns regardless of a good bath. I have heard of guys using sunlight to get rid of the frosting but be cautious not to melt your figures leaving them out on a super sunny hot day.
I have caviar dreams and McDonald's pockets