The Standard Life GB men were defeated by Macedonia as they lost 78-67 in Ankara, Turkey.
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Flinder Boyd returned to the roster but Joel Freeland was counted out due to an intestinal illness.
Nick George again top scored, with 14 points, Andy Betts was the only other Brit in double figures with 11 while Robert Archibald had 9.
Head Coach Chris Finch said: "It was really poor, for the first time I thought we played pretty uninspired."
"We have been playing hard and competing, but tonight we couldn't do any of that which was frustrating because the game was there for us to win.
We have a lot of work to do before Poland. The first thing is to get everybody fitter and then after that we have to learn how to make each other better and play through the tough times."
However Finch tried to remain positive "We know we can go to Poland and beat anybody on the day."
Macedonia are in Group A of the European Championships, alongside Israel, Croatia and Greece. Britain will now return to the UK for final preparations, before they head to Poland.