The 47-year-old told his co-host Jackie 'O' Henderson that the former celeb couple used to come over to his house and play a little game where they would spit in to each other's mouth.
"I remember when I'd have them around my house and they were in love and sometimes would spit in each other's mouth," explained Sandilands.
Reacting in shock, Jackie O exclaimed, "Why?"
"Fun, they said fun," replied Kyle, "But I always thought, 'Wow! That's weird'."
Kyle went into further detail by revealing that, "Delta would sit with her mouth open and Brian would spit into her mouth and Delta would spit back into his mouth,"
"You would think they're all good. He's English and she's Australia's sweetheart, but at my place [Kyle makes spitting noise] 'I got her!', and I was like, is that love?" continued Kyle.
"I think that's gross. I think I'd throw up if someone spat in my mouth," responded Jackie O in disgust.
After recording the duet Almost Here in 2004 for Delta's album titled Mistaken Identity, the two singers begun to date.
They later became engaged in 2007 during a trip to Bali but split up in 2011.
Delta opened up to Vogue about her break-up from McFadden and said, "I was really unhappy and didn't know how to get out."
She also spoke to 60 Minutes and revealed that she wished the relationship had ended earlier than it did but she lacked the courage to do so and that the cause of their split was due to them being "very different people - extremely different people."
Following her two interviews, Brian took to Twitter to post, "Sometimes silence in golden. People love to try and deflect attention from their own downfalls onto others."
Both Goodrem and McFadden have since moved on with other people. McFadden, 38, is currently dating Danielle Parkinson, who is a PE teacher. Meanwhile, Delta has most recently been linked to rock singer Matthew Copley.
Delta has publicly revealed before that she prefers to keep her dating life private.