Khalaf al-Hosany, their lawyer, told the court in a previous hearing that they kissed on the cheek as a greeting and "never intended to break the law".
The case is the third time in under two years that Britons have fallen foul of indecency laws in Dubai.
When in Rome
Mohamed al-Mutawa, a professor of sociology at Al-Ain university in the UAE, said Dubai is an open society, but visitors must follow the rules.
"There is a saying: If you are in Rome, behave as a Roman. Anyone coming to Arab countries has to respect the law there and the customs of the people there," he told Al Jazeera.
"Behaviour which previously people would have turned a blind eye to is now causing controversy"
Christopher Davidson, analyst on Dubai
He rejected the suggestion that Dubai, which has some of the most relaxed social codes in the Gulf, is sending mixed messages with Sunday's ruling.
"The message is: behave [according to] our customs, our religion and our law and you are welcome."
Najafi, who works in Dubai, and Adams, who was visiting the UAE as a tourist, were also fined 1,000 dirhams, or about $270, for illegal consumption of alcohol.
The pair has 30 days to appeal Sunday's ruling in a higher court. If their appeal is rejected, they are to be deported after serving their sentences.
Christopher Davidson, an analyst on Dubai at Durham University in the UK, said the case is a blow to Dubai's reputation as a holiday resort.
"This is yet another incident in Dubai signifying the growing tension between the local population and the expats and tourists," he told Al Jazeera.
"When Dubai was booming and the economy was strong, money was going into people's pockets, so people tended to get along. But since the recession hit Dubai, the tensions have come to the fore and various communities are struggling to get along.
"So behaviour which previously people would have turned a blind eye to is now causing controversy.
"[Dubai] needs its economy to continue bringing in the tourists but on the other hand it needs to play very carefully with the sensitivities of the local population."
Millions of Western tourists visit the emirate each year. Although Dubai law forbids public showings of affection, prosecutions are rare.
Last month, an Indian couple was sentenced to three months in jail in Dubai for exchanging sexually explicit text messages.
In 2008, two Britons accused of having sex on a beach in Dubai were sentenced to three months in jail, though their sentences were later suspended.