Physician Ahmed Said was among those whose appeal was rejected on Wednesday.
An Egyptian court rejected the appeal on Wednesday by four 6 of April members against their two-year jail sentences on charges of protesting illegally in November 2015.
In December 2015, a Cairo court sentenced the four members of the now-banned group to prison for protesting illegally and using fireworks as a weapon on the fourth anniversary of the Mohamed Mahmoud clashes of 2011.
The defendants argue that they were holding a peaceful stand on the 6th of October bridge in November 2015 to commemorate comrades who died in the Mohamed Mahmoud clashes.
The defendants included Ahmed Said, a one-time Egyptian resident in Germany physician whose case attracted international attention.
Many of the movement's members, including founders Ahmed Maher and Mohamed Adel, are currently serving prison sentences for violating the protest law.
Egypt’s protest law, which was passed in November 2013 following the ouster of Islamist president Mohamed Morsi, stipulates jail sentences of one to three years and fines for participants in unauthorised protests.
April 6, which was founded in 2008, played an important role in fomenting the 2011 uprising against then-president Hosni Mubarak.
The group was named after the day a mini-uprising that took place in the industrial city of Mahalla against Mubarak.
The movement was often targeted by authorities before the uprising but was given a respite after the toppling of Mubarak.
However, since the ouster of Morsi, several Egyptian media outlets have denounced the movement, which opposes both the Muslim Brotherhood and the post-Morsi authorities.
In December 2014, an administrative court outlawed the group.
On Monday, which marked the fifth anniversary of the January 2011 uprising, the movement issued a statement saying it will continue its "efforts in reuniting the revolution's political factions to reclaim its goals, especially since the ruling regime has showed its suppressive practices against the people."
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