If the tank needs to be deep cleaned (eg it held fish with a very infectious disease and you want to make 100% sure) you can use dilute bleach - cheap supermarket basic range bleach which contains no surfactants or perfume, or baby bottle sterilising solution, all diluted 1 part bleach and 9 parts water. Rinse very thoroughly with water then a final rinse with water overdosed with dechlorinator.
The same can be used for equipment, though I wouldn't recommend bleach for a substrate; I would just throw that away.
But for most diseases, a thorough wash and scrub then allowing the tank and equipment to dry will kill most fish pathogens. They can't survive being dried out. But if you are thinking about lymphocystis, I admit that I did bleach the the tank and equipment that the infected betta was in to be on the safe side. I threw away the filter media and did a fishless cycle before getting the next betta. I'd never actually done one before!