The Black Hawk Down star claims the odd couple enjoyed a torrid drug-fuelled romance and details it in his memoir By Some Miracle I Made if Out of There, admitting he eventually had to leave.
As part of a week of candid confessions on U.S. news show Access Hollywood, the actor, who has battled substance abuse for almost two decades, says the Natural Born Killers star was a "raw talent" with a penchant for hard drugs and porn movies.
He says, "She bought a house... and so we go there and we moved into the bedroom and we were in there for a long time and I went outside the room one day and I walked around and I said, 'Juliette, you live in a really big house here, we should furnish it,' and she went, 'Why...?' When I went to take a shower, she went, 'Can I come with you?' We were on drugs, whatever... But she was really charming. She was 19 years old.
"I was there for four months - in that room... She had one of the big Tvs... and she played porn... every day, all day. She went, 'I like the music'."
In his book, Sizemore also claims he romanced fellow actresses Elizabeth Hurley and Edie Falco. None of the women have so far commented.