The Chemnitz local, who was not named, was also fined €2,000 over his action on September 1st.
The penalty was more lenient than the one-year prison sentence sought by prosecutors, who are examining whether to lodge an appeal.
Thousands of demonstrators had answered a call by the far-right party AfD and the Islamophobic Pegida street movement to march over the fatal stabbing of a man, allegedly by asylum seekers, on Sunday August 26th.
During the heated rallies, a handful of people were seen publicly making the illegal salute, while others were shouting anti-foreigner slurs.
Police have been investigating the cases and last week said they had identified six people who they believed had made the sign.
The district court in Chemnitz has implemented fast-track criminal procedures in order to process all the suspects charged with violating Germany's hate speech laws.
A 34-year-old man is due in court on Friday over a similar charge.
The swastika and other Nazi symbols are banned in Germany. Those caught breaking the law can be fined or face a jail term of up to three years.