After a less experienced GB line-up lost 90-62 behind closed doors on Saturday, coach Joe Prunty restored his frontline players for Sunday's game.
The resulting 78-69 defeat, with Andrew Lawrence top-scoring with 15 points, gave a better indication of GB's improvement this summer.
Their next game comes against Greece at the Copper Box in London on Saturday.
Kavell Bigby-Williams, one of the finds of the summer programme, had 16 points and took 11 rebounds on Saturday as the newer members of squad struggled to match their more experienced hosts.
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On Sunday, the return of starting centre Dan Clark, scoring guard Lawrence and forward Gabe Olaseni had GB in front for most of the first half.
Israel took command of the game with an 18-6 run in the third quarter and although GB closed to 73-66 down with three and a half minutes remaining in the game, a series of missed shots prevented them taking advantage of the opportunity.
"We're improving every week," said GB assistant coach Nate Reinking. "We're coming to London and hopefully we get a great week of practice and we keep doing that, because the goal has to be to peak at the end of August."
Great Britain suffered back-to-back defeats to Israel in Tel Aviv in their latest EuroBasket warm-up games.