Reece Hardy, 27, gave the victim the Valium while they were out in Scarborough, and when she passed out he raided her purse and took out her bank card, keys and Â£25 in cash, York Crown Court heard.
An ambulance was called and while the victim was being transported to hospital, Hardy withdrew Â£75 from her account using the stolen bank card.
Prosecutor Victoria Barker said the victim, who was named in court, woke up in hospital to discover all her bank cards were missing.
Hardy was arrested and charged with theft from the person, fraud and breaching a suspended prison sentence. He admitted the offences and appeared for sentence via video link on Monday.
Ms Barker said Hardy had met up with his ex-partner in Scarborough town centre on November 15 and they went for a drink in a local pub where he handed her a Valium tablet which she swallowed.
“That resulted in her passing out,” added Ms Barker. “The defendant goes into her purse and takes out Â£25 and a number of her bank cards and keys.”
She said Hardy withdrew Â£75 from a cash machine, in three separate withdrawals, even before the victim arrived at hospital at about 7.30pm.
Ms Barker said that Hardy, of Lonsdale Road, Scarborough, was on bail at the time after being previously arrested and charged with an alleged criminal-damage offence in September. Part of his bail conditions was not to contact his ex-partner.
The shocking offences occurred just a week after Hardy had been convicted of assaulting a teenager with learning difficulties in Scarborough town centre in July.
The 16-year-old victim, who cannot be named for legal reasons, was walking in St Thomas Street where two males, including Hardy, were grappling in the street.
The teenager tried to walk past the scuffle just as Hardy threw the other man into some railings. But then Hardy then turned his ire on the teenager, punching him in the side of the face in what was described as a “completely unprovoked” attack.
The teenager ran off crying. He was not seriously injured but suffered pain and soreness to his face. He found some police officers nearby and took them to Hardy, who was arrested.
Hardy told police he had drunk 10 pints of beer and three bottles of cider. He claimed he had been set upon by a group of men in the pub and may have confused the teenager as being part of that group.
Ms Barker said the teenager had since been “scared about going out, particularly into Scarborough town centre”.
Hardy had previous convictions for drink-fuelled violence, public disorder, resisting a police officer and shoplifting. In April 2017 he received a suspended jail sentence for wounding and criminal damage.
David Camidge, for Hardy, said his client’s offending was fuelled by alcohol, adding: “Quite clearly, he has problems with alcohol misuse.”
Jailing Hardy for 16 months, judge Simon Hickey said he had taken advantage of his ex-partner after she had passed out, which he branded an “extremely mean, disgraceful” offence.
And he slammed Hardy for attacking a teenager with learning difficulties who was “minding his own business”.