Four young suspects – who were arrested during major anti-government protests in August – collapsed on the courtroom floor, writhing in pain before being removed to get medical help.
Human rights activists have criticised the justice system as at least one-third of those brought in for the initial court hearing were boys aged between 14 and 18.
All 76 defendants pleaded not guilty to charges of treason, felony and inciting mutiny.
Activists said the defendants had been in custody since August, when protests over a deepening cost-of-living crisis ignited across Nigeria.
The demonstrations turned violent in some places as protesters clashed with security forces. At least seven people died, according to police, though rights groups have put the death toll at 23.
There were also nearly 700 arrests.
In response to Friday’s dramatic court hearing, which took place in the capital, Abuja, rights group Amnesty International said: “Putting minors through these horrifying detentions for participating in protests against hunger and corruption is – so far – one of the deadliest attempts to suppress freedom of assembly.”
A Nigerian rights organisation, named Enough is Enough, called the situation “institutional child abuse”.
“These teenagers have been remanded in prison for saying they were hungry. Their place is in school, not prison. Release them now,” the organisation demanded.
Some of those who appeared in court on Friday were charged with flying Russian flags during the protests.
Video footage of the demonstrations showed a small number of protesters waving Russian flags and calling on Russia’s President Vladimir Putin for help.
Two months ago, 10 other suspects appeared in court, charged with treason and other serious offences.
They were accused of working with a British citizen “to destabilise Nigeria by calling on the military to take over government from President Bola Ahmed Tinubu”, according to the charge sheet.
All of the suspects in this case pleaded not guilty.
In total, 114 of those arrested during the protests were charged with treason. A judge has granted each of the defendants a 10m naira ($6,000; £4,700) bail.
Nigeria is experiencing its worst economic crisis in a generation – annual inflation stands at more than 30% and food prices have rocketed.
