Geleto Kabeta Daledu Eggu pleaded guilty to two charges of assaulting a police officer without occasioning actual bodily harm on Tuesday in Sydney's Downing Centre Local Court.

The 22-year-old had joined 20,000 who marched on June 6, 2020, in support of American George Floyd who had been recently killed by police, and Indigenous man David Dungay who also died in Australian custody.

A last-minute decision by the NSW Court of Appeal authorised the public gathering which moved from Town Hall to Belmore Park and Central Railway Station where police attempted to disperse the crowds.

But as large groups of people continued "loitering and chanting," Eggu displayed an angry demeanour and was pushed by an officer and told to "move back," according to court documents.

The Mount Druitt man then threw a plastic water bottle from about five metres away at one officer who said it felt full or partly full, and a Kinder Bueno wrapped chocolate bar at another.

Shortly after Eggu was arrested for separate offences "committed within the continuity of disruptive crowd behaviour," but was granted strict conditional bail.

Magistrate Sharon Freund acknowledged the worldwide heightened police and civilian tensions surrounding the protest and the confined Sydney train station space where the conflict escalated.

"In terms of criminality, it would have to be at the lower end of seriousness, the throwing of a partially filled water bottle and a small chocolate," she said.

But the judge said officers performing frontline duties deserved extra protection in the community and were not to be assaulted under any circumstances.

Eggu's lawyer Ben Jamieson earlier indicated that his client would be pleading not guilty. But after viewing body-worn camera footage for the first time this was changed and accepted by Ms Freund as an early plea warranting a reduced sentence.

He was given a 12-month conditional release order expiring in May 2022.

Australian Associated Press