The men aged between 27 and 37 must pay between 300 and 1,800 euros ($336-$2015) for infringing laws against wearing uniforms, the Wuppertal tribunal found.
Germany's laws against wearing uniforms originally aimed to prevent neo-Nazis staging rallies and parades.
Judges said the group's actions were aimed at achieving an "intimidating effect suggestive of militancy" by aping the sharia police that exist in some Middle Eastern countries as violent organisations.
In September 2014, the seven patrolled the streets of Wuppertal, a west German industrial town with a sizeable Muslim population, wearing orange high-visibility vests marked "Sharia Police".
When they encountered young Muslims, they told them not to drink alcohol or visit cafes, betting shops or brothels.
Monday's verdict comes at the end of a second trial for the group after the constitutional court last year overturned their 2016 acquittal.
At the time of the "sharia police" patrol, the men were led by one of Germany's best-known fundamentalist preachers, Sven Lau, a 38-year-old convert to Islam.
He was himself sentenced in 2017 to a five-year jail term in a separate case, after being found guilty of "supporting a terrorist organisation" by recruiting potential jihadists to travel to Syria.