Nineteen-year-old Wayne Christopher Carroll, of Brooklyn, Clement Road, Goodwick, was disqualified from driving for 12 months and fined £150 after he admitted taking the red Ford Fiesta last Wednesday.
He was also fined £100 for using the vehicle without insurance and will have his licence endorsed with six penalty points.
No separate penalty was imposed in respect of a further charge of driving otherwise than in accordance with a licence, but Carroll, who works as a labourer, was ordered to pay £30 costs.
The court heard how the defendant, a provisional licence holder, his co-defendant, Scott Andrew Waugh, and a third person, who was not charged, had been to DJs nightclub in Penally.
A friend was going to give them a lift home, but let them down and as a result they found themselves in Tenby, where they were planning to stay in bed and breakfast premises, but 'foolishly' they broke into the car, Carroll's solicitor, Mr. Paul Cowper, told the court.
The car would not start, but rolled 10 yards, before stopping across the road.
Twenty-one-year-old Waugh, who pleaded guilty to an offence of allowing himself to be carried in a vehicle taken without consent, told the bench it was a "moment of madness."
"It was stupid; we were soaking wet, freezing and not thinking straight," he said.
Waugh, of 85 Harriet Street, Cathays, Cardiff, was fined £150 with £30 costs.