Jordan James Fineanganofo did not attend Parramatta Bail Court on Saturday where his lawyer, Javid Faiz, did not apply for bail and it was formally refused.
Steven Tougher, a 29-year-old father of one, was stabbed outside Campbelltown McDonald's when he and a workmate took a break towards the end of their night shift about 5.30am on Friday.
The colleague activated an alarm, sparking a police response in which a man wielding a knife was tasered and arrested.
Homicide detectives later charged Fineanganofo with murder.
Outside court Mr Faiz told reporters his client had mental health issues and was in the hospital at Long Bay jail, but he understood the charges.
"I've explained the offences and he is fully aware of the gravity," he said.
Mr Faiz separately told AAP he understood his client had been undergoing extensive mental health treatment but was not receiving treatment at the time of the incident.
"I believe he was off treatment and medication at the time," Mr Faiz said.
"He was confused all last night but is doing better today," he added.
Fineanganofo is due to reappear in court on June 28.
Mr Tougher, who had been working for the ambulance service for about a year, died shortly after arriving at Liverpool Hospital.
A GoFundMe page set up on Friday afternoon sought support for the paramedic's partner Madison who is expecting a second child.
It is understood the couple intended raising their family in southwestern Sydney after he recently landed a posting in the area.
Mr Tougher's family said he would be remembered for his compassion, kindness and ability to connect with people "with genuine warmth and empathy".
"Steven's compassion touched the lives of so many people," a statement issued on Saturday read.
"He was always ready with a smile, a kind word, or a lending hand and brought joy to those around him."
Prime Minister Anthony Albanese paid tribute to Mr Tougher on Twitter on Friday, calling his death "as shocking as it is tragic."
Dozens of flowers and cards have been laid at the crime scene as friends and family described the young father as a "beautiful soul" in tributes across social media.
One letter left by a retired paramedic read: "Prayer to you, brother. Your shift has ended. Rest in peace".
Another tribute by fellow paramedic Amanda Russell to the GoFundMe page said Mr Tougher's service would not be forgotten.
"My husband and I, both paramedics, have sat in that same carpark doing that exact same thing many many times," Ms Russell said. "Steven your service and sacrifice will never be forgotten."
Emma Gedge, a union branch official who worked with Mr Tougher when he worked as a registered nurse, said his legacy would live on.
"We will never forget his big smiles, cheeky giggles and charismatic personality," she said. "For his new wife, your husband was an amazing guy, and his legacy is going to live on in his kids."
The NSW Nurses and Midwives Association - where Mr Tougher worked as a nurse before becoming a paramedic - described him as "a true hero with the kindest soul".
"It's heartbreaking when a healthcare worker doesn't get to go home. Nurses and paramedics live our lives to help others. This is just senseless," NSWNMA general secretary Shaye Candish said.
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