Gruekvski, who dominated the Balkan country for nearly a decade until 2016, was convicted in May of using the 600,000 euro Mercedes for personal travel even though it was purchased with state funds.
The Skopje court said it found "the complaints of the accused... unfounded, and confirmed the first instance verdict in full."
Speaking to AFP, special prosecutor Gavrilo Bubevski said Gruevski has a two-week deadline to turn himself in to prison.
"It is a matter of days. It can happen today or tomorrow or in 15 days," said the prosecutor.
But the former premier told local media he would use "all legal means to fight the prison sentence".
"This is just another attempt at political prosecution," he said.
Gruevksi, who led the right-wing VMRO-DPMNE party, resigned in 2016 after a scandal emerged over tapes that appeared to show a widespread wire-tapping scheme by his administration.
He now faces a number of graft cases, with the Mercedes charge the first to go to trial.
The verdict comes at a tense political moment in Macedonia.
A new ruling coalition is trying to push through a deal to change the country's name and end a long-running row with Greece that has hampered its Western integration.
A referendum on the new name -- North Macedonia -- was approved by more than 90 percent of voters last Sunday but undermined by low turnout.
VMRO-DPMNE, now in the opposition, is calling the poll invalid and blocking Prime Minister Zoran Zaev's attempts to sway two-thirds of parliament to ratify the deal struck with Athens.
While in power Gruevski took a hardline stance against the name dispute with Greece, which has its own province called Macedonia.
Athens has blocked Skopje's entry into NATO and EU over the issue for nearly 30 years.
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