Nonoxynol-9.
Dishwasher soap
Sperm is killed when it is outside a human. When trying to enter an egg, most of the sperm will die.
Once they are inside the vagina there is only one thing she can do and that is to take the morning after pill. If it's on your hand wash it off or it will die when dry. Someone wrote urine kills...
yes, staying in a hot place like kitchen(near oven) may kill your sperms but it is a little rare so make sure you don't stay in near heat for long