What is it that you want to kill? With geckos and in life, if we eliminate every possible germ we also reduce our ability to develop resistance to germs. When I clean my cages I use water, then hydrogen peroxide, then vinegar (spraying each and wiping each application up after 30 seconds. Everyone is fine except for the fact that they're all crypto positive, but there's nothing I could have done in terms of disinfecting to prevent that unfortunately.
I am sorry to hear your geckos have crypto My Leo actually has pinworm (from breeder) that I am treating. I am trying to prevent that from happening again the best I can. I have just tried wiping down the glass and hides with water & dawn dish soap and then with Chlorhexidine.