Is there a food that can kill sperm in the woman's uterus?
There's no food or supplements that will act as a contraceptive or disable sperm in the uterus.
If you want to avoid pregnancy you should go on a reliable form of contraception. This can be hormonal: The pill, patch, ring, implant, injection or hormonal coil (IUS) or non-hormonal like the copper coil (IUD) or diaphragm. You can also use a barrier method like condoms (female and male).
If you have unprotected sex you can take an emergency contraceptive tablet up to 72 or 120 hrs post pregnancy risk which delays ovulation and can prevent pregnancy.