A driver on the M50 threw a large bottle of cola at a woman driving a convertible in a fit of road rage because she was driving too slowly.
Daniel McDonagh (23) claimed the female driver was "doing about 15kph" as she came on to the motorway, and he threw the bottle in frustration. The woman had the top down on her convertible and the bottle hit her in the face, temporarily blinding her.
The drink spilled all over her and the car, the court was told.
Judge Anne Watkin said the matter was very serious and McDonagh could have killed the woman or other road users.
The judge ordered a probation report and adjourned sentencing to May.
The defendant, of Oldcastle Drive, Clondalkin, admitted criminal damage at Junction 13, Dundrum, on June 24, 2017.
A state solicitor told Dun Laoghaire District Court that the injured party was driving on to the M50 from Dundrum when McDonagh came up behind her and started beeping and gesturing at her to go faster.
She could not go any faster because there was a car in front of her.
McDonagh then pulled over on to the hard shoulder as traffic entered the motorway and hurled the large plastic bottle at the woman. Although momentarily blinded, she was otherwise unscathed.
However, the cola sprayed all over her clothes, over the car seats and caused some damage to the car's electrics.
The vehicle also had to be professionally cleaned. The damage - including the cost of dry cleaning the victim's clothes - ran to €591.
After throwing the bottle, McDonagh drove out in front of the woman and on to the fast lane, the court heard.
The victim took photos of McDonagh's van and the registration number and he was later identified as the culprit. He was interviewed by gardai and made admissions about his behaviour.
The court heard McDonagh had seven previous convictions.
Defence lawyer Miranda Egan Langley described it as a "moment of madness".
He was frustrated that the female driver was going slowly and made some hand gestures to her to go faster.
McDonagh, a married fath-er-of-one, accepted he was completely in the wrong, the lawyer said.
"She was doing about 15kph on to the motorway," McDonagh interjected. Judge Watkin told him she did not care if the victim had been doing 5kph, and he was lucky no one had been killed.
Ms Langley said the defendant had problems with cannabis and had been trying to stop. He believed the withdrawal symptoms made him prone to bouts of anger, she said. McDonagh admitted he had also taken cocaine and tablets of the sedative benzodiazepine in the past.
As well as a probation report, Judge Watkin ordered him to take a urine test.