The supermodel and the X Factor judge, together with Packed to the Rafters actress Jessica Marais, stripped down to swimwear for the cover of Who magazine's annual Sexiest People issue.
Hawkins revealed the secret to her and boyfriend Jake Wall's chemistry, saying: "Wearing a beautiful G-string under your dress is sexy. I love wearing matching sets - to me, that's sensual.
"[We have] always had the spark and I think once you've got it, it's easy to keep. You've either got a connection with someone or you don't. Having that sexual chemistry is a big tick."
Marais said of her recent engagement to co-star James Stewart: "Getting engaged has been amazing - there's something about the freedom that comes with that kind of security that's really sexy, because there's a lot of trust."
Meanwhile, Imbruglia insisted that she is "just friends" with rumoured boyfriend Justin Hemmes and revealed that she is looking for "a sense of humour", "confidence" and "magnetism" in a man.