The man was seen smoking outside the Bizerte courthouse by a judiciary official who informed the police before they arrested him and referred him to the prosecution, the spokesman Chokri Lahmar told AFP.
He said the man had 10 days to appeal before the sentence takes effect.
On June 1 four men were sentenced to one-month jail terms for eating in public during Ramadan.
There is no law against eating or drinking in public during Ramadan, but every year the issue comes to the fore in the North African country.
Tunisia’s constitution guarantees “freedom of belief and conscience”,
but the state is also the “guardian of religion”.
Monday’s ruling came a day after dozens of Tunisians demonstrated in the capital Tunis to demand the right to eat and drink in public during the Muslim fasting month.
During Ramadan, Muslims around the world abstain from eating, drinking, smoking and having sex from dawn to dusk.
They break the fast with a meal known as iftar and before dawn they have a second opportunity to eat and drink during suhur.