The containers often pick up dust while sitting around. I often relieve my mind by just rinsing off the container and then dunk the sealed container into a bucket of starsan and let it air dry for a few minutes before use. If it has been opened before and you want to sanitize the opening, then try a few alcohol wipes to get the edge of the opening clean and sanitized again.
I also use an alcohol wipe (bottle of isopropyl alcohol and a paper towel works OK, too) to wipe down the outside of yeast smack packs, scissors blades, and even the outside of spigots and various attachments.