Defender Sinnamon was one of four young Gers players who started the 5-2 victory over Luxembourg today.
He completed the full match along with goalkeeper Liam Kelly and forward Danny Stoney while midfielder Tom Walsh played for an hour before being replaced.
Scotland were already comfortably in control but Sinnamon grabbed the goal of the game with a sensational 40 yard left foot effort in injury time to send the Scots top of the group.
The victory gets the young Scots off to the perfect start in Georgia where they compete in a four team round robin competition.
They top the group after the first round of games with Ukraine beating hosts Georgia 3-1 in the other match.
The Scots will now face off with Ukraine on Thursday before wrapping up the week long challenge against hosts Georgia on Sunday.