From March 2022 to September 2023, Dr Sak served as an external advisor to the Minister of Defense of Ukraine.

Following that, in December of 2023 he was appointed as an external advisor to the Minister for Strategic Industries. 

In March 2014, he co-founded the Ukrainian Crisis Media Center (UCMC), where he worked until 2018 as a press event moderator and coordinator of international projects aimed at promoting Ukraine's interests on the international stage. Specifically, he was involved in the development and execution of international projects focused on strengthening global support for Ukraine in countering Russian propaganda in the temporarily occupied territories of the Donetsk and Luhansk regions, as well as in the temporarily occupied Crimea. 

In 2006, Sak began working at CFC Big Ideas, specializing in strategic communications and public relations. 

From September 1999 to July 2000, he pursued further studies in international law at the University of Oxford, United Kingdom. Subsequently, from September 2000 to September 2006, he completed his PhD program at the University of Wolverhampton, earning a PhD in international law. His dissertation was titled "The Right of Internally Displaced Persons to Return Home After Military Conflicts." In July 1994, Sak enrolled in the Institute of International Relations at Taras Shevchenko State University of Kyiv, graduating in 1999 with a master's degree in international law.