In the middle of 2006, Sivok became a main face of a Czech government anti-racist campaign which is called Together Against The Racism.
He has signed for Udinese during the January 2007 transfer window. It is believed that Udinese paid Sparta Prague a transfer fee in the region of 2.5 million pounds for Sivok's service and Sivok put pen to paper in a 4 and-a-half years contract until the summer of 2011. In May 2008, he was sold by Udinese to the Turkish side Beşiktaş J.K. for €4.7 million. He signed a four-plus-one-year contract worth €800,000 per season and up to €100,000 in bonuses; his salary would raised to €1.2 million if he extends his contract to 2013.
He is well known as the 'Golden Head' amongst the Beşiktaş fans due to his dominant capability of scoring headers from set pieces.