This prompt is the kinky lovechild of the comment asking why Nicky and Joe had medical drapes over their groins and fanfics where the lab creates a child from their sperm.
Kozak wants sperm samples from them, so she uses electroejaculation on Nicky. A method where a probe is inserted anally to stimulate the prostrate. Usually done under anaesthetic as it would be quite painful and causes muscle spasms. You just know she wouldn't be bothered about that. Keep it clinical and medically detached. It can just be him and her, or she can have an assistant.