After ejaculate inside, what to do to wash away sperm for hygienic purposes not to get infection(im not concerned about pregnancy cause im on yaz)?

A vagina self-cleans: Vaginas are designed to be self-cleaning. It is not natural to be washing the inside of a vagina, but once in a while may be ok. If bacterial vaginosis is a problem, one might do better if she keeps semen out of her vagina for a while, to allow her vagina to naturally self-clean and maintain normal acidity ; normal microbes. Frequent sex is fine, but using condoms to contain the semen each time.