Allahyar, who played on loan in Istanbulspor for half a season last year, could not score a goal and assisted in four games he played with Fenerbahçe.
Sayyadmanesh joined Fenerbahce last year from Esteghlal on a five-year deal but failed to meet expectations.
The 20-year-old forward was a member of Iran football team who qualified for the 2017 FIFA U-17 World Cup quarter-final in India.
He made his Iran national football team debut on June 6, 2019 against Syria and scored a goal.