A man approached a woman who was masturbating on a train, received oral sex from her, before washing his genitals with Coca-Cola.

The train traveller was on Tuesday convicted over the bizarre incident on the 9.56am service from Port Kembla to Wollongong, south of Sydney, in December.

'I got a blow job on the train and I was rinsing my c**k off,' he told police who stopped him at Wollongong Railway Station, the Illawarra Mercury reported.

The man reportedly approached the masturbating woman, before she began performing a sex act on him after a brief interaction.

A man approached a woman who was masturbating on a busy train, received oral sex from her, before washing his genitals off with Coca-Cola (stock image)

City Rail staff discovered a 'large and disgusting' mess on the floor which they initially believed was urine.

'I wasn't having a piss, I spilled my coke... it's just coke,' he said to police, telling them he used the drink to 'clean himself up' after the sexual encounter.

The woman involved, who the paper reports is well-known to police, confirmed the man's version of events.

He pleaded guilty to charges of offensive behaviour and obscene exposure at Wollongong Local Court on Tuesday.

'The facts speak for themselves... he took the opportunity that presented itself,' his solicitor told the court.

The man was placed on a 12-month good behaviour bond and fined $700.