The 36-year-old, whose book is set to be published by Kees Jansma on Friday, joined the Spanish side from Ajax in 2007 for €27 million for a two-year spell before he was sold to Inter Milan for €15m.
He said: "I was young and enjoyed the success and attention.
"It must have gone wrong there -- later. No drugs, but alcohol and 'rock-and-roll'. I got used to that, as one of the stars... You are worshipped as a Real player.
"All your mis-steps are instantly forgiven because of your status and popularity. Even if I rolled over the street and spent thousands of euros, or gave rounds to the whole bar. I cannot say that I resisted enough."
In the book, Sneijder reveals the reasons for his first divorce: "I was left alone and didn't see the little one, Jessey, much, that was s---. And I'm bad at being alone. Why would you even be alone when you have enough friends to spend your time with.
"I just didn't realise that the bottle of vodka became my best friend."
The club and his fellow teammates Arjen Robben and Ruud van Nistelrooy, encouraged Sneijder to change his lifestyle: "I played pretty well, but they said I could do even better," but to no avail. In his own words he describes his performance during the last season there as "unworthy."
"I still played a lot, but not so good and sharply, less concentrated. My attitude was unworthy of Real Madrid. I lied to myself that it was going well and I held my own by my football intelligence. Physically I deteriorated. I ran less, covered up a lot with my technique and my kicking technique. I also thought no one noticed."