The 32-year-old pleaded guilty to common assault and criminal damage at North Tyneside Magistrates' Court on Tuesday and was fined £520, including £350 compensation for Mr Farage.
Speaking to LBC on Wednesday, Crowther said the attack wasn’t pre-planned and wasn’t “the right thing to do”.
Recalling the incident, he told presenter Nick Ferrari: “I’d gone for a milkshake. I was on my way back. I had seen a Brexit rally. Then he emerged from the crowd.
“I don’t think anything went through my mind. It was a total loss of any kind of rationality or logic.
“I do [regret my actions] and I do want to apologise to Mr Farage for what I did.”
Crowther, who lost his job as a result of the attack, went on: “Despite my feelings about the man, logically would I say that’s the right thing to do? No, I wouldn’t.
“I’m a very strong believer in democracy and the right to speak and I absolutely regret what I did.
“I hadn’t been drinking, it was 12 o’clock! The only thing I had been drinking was milkshake.”
The incident came during a spate of milkshake attacks on right-wing candidates including Ukip’s Carl Benjamin and English Defence League founder Tommy Robinson.
Mr Farage said afterwards that “normal campaigning is becoming impossible”.
Prosecutor James Long told the court on Tuesday that Mr Farage would not have known “whether it was a harmless liquid or something, in this day and age, far more sinister”.
An online fundraising page to pay Crowther’s court costs has raised more than £1,700.
Graeme Rayner, who set up the page, said Crowther supports the fundraising.
Mr Rayner added: “Throwing a milkshake over someone is, in my opinion, relatively harmless.”
The Standard has approached the Brexit Party for comment on Crowther's apology.