The 65-year-old actor was married to the model-and-actress for two years from December 1985 and the Danish beauty says he was like "a rabbit" when they had sex and also admitted his steroid use had had an unfortunate side-effect.
During a chat on 'Ich bin ein Star - Holt mich hier raus!' - the German version of 'I'm a celebrity... Get Me Out Of Here!', Brigitte spoke of the actor's steroid use, prompting former T V presenter Ramona LeiÃ to ask her: "Don't your balls shrink when you take steroids?"
Brigitte laughed and said: "Yes, yes, yes!"
Pressed on whether he was good in bed, she added: "No! He was like a rabbit."
The 48-year-old star also discussed how the 'Rambo' star changed after they married, admitting he was very possessive.
She said: "A day after we married he was a completely different man. I was like his car. It was horrible."
Sylvester has previously admitted he had a "temporary form of insanity" during his relationship with Brigitte.
The 'Rocky' actor has been happily married to former model Jennifer Flavin since 1997, and the pair caught footage of his ex-lover when she appeared reality show 'Celebrity Rehab with Dr. Drew' in 2008 for problems with alcoholism.
He recalled: "I thought I was watching an old home movie. I sat on the sofa with Jennifer and of course, she pauses it and says, 'What were you thinking?' I go, 'I wasn't. It was an out-of-body experience. I've concluded that love is a temporary form of insanity and we should cut each other some slack.'
"I consider my life 10 per cent on target, and 90 per cent mistakes. But those 10 per cent counted."