Down 25-12 after the opening period, Finch's men had no answer to the powerful Turks and could not produce the same dogged display as in the teams previous meeting in London two weeks ago.
The hosts, recovering their form, pulled 45-22 ahead at half-time and extended the gap with an 8-0 run that secured a 66-31 cushion at the end of the third.
With GB's guards lacking any penetration, and the bigs growing in frustration, the deficit increased to as much as 41 points before Jarrett Hart - who hit a team-best 14 - sparked a late flurry as Turkey threw on their reserves.
GB now return to London to complete their preparations for Poland and are still awaiting news of whether the saga over Pops Mensah Bonsu's absence will be resolved. With one or two cuts remaining before the final 12-man squad is announced, Finch will have some tough calls to make.
Assuming the newest arrival at the Houston Rockets is ruled out, Dan Clark, despite his huge progress, may lose out to the versatile Achara for a frontcourt spot even after his 7 and 11 rebound showing against the Turks. While Nate Reinking or Germayne Forbes are the most likely casualties in the backcourt.
Finch's greatest concern, however, is two lacklustre displays and the lack of time to find a remedy with GB finishing their warm-up campaign with a miserable 1-8 record.
Tournament stats are here.