How long would sperm live in your mouth if you had oral sex on a friday, and you have eaten and drank normally 4 days later?

Sperm can live ~4 -5 days under the best environmental condition provided by a woman's vagina/cervix/womb and Fallopian tubes. The environmental conditions in the mouth would neutralize these within minutes, rendering them unable to do anything but die. Four days later their protein & fluid content would have been digested and recycled.

Sperms die within ten minutes of ejaculation if not in the proper environment (vagina)