Dale Boulding's victim, who suffers from various degenerative brain diseases, was admitted to hospital for around a week in May 2016 due to problems caused by his conditions, Sheffield Crown Court heard.
During this time, Boulding, aged 33, came into possession of the man's bank card and made 21 transactions, withdrawing a total of £6,955 David Wain, prosecuting, said.
The two men are believed to have met each other when accessing alcohol dependency services, the court heard.
Mr Wain said: "After the transactions were made he moved on to Skegness, where he was discovered by police in November 2016.
"The Crown would say it's a deliberate targeting of someone he knew to be vulnerable."
Mr Wain told the court Boulding's victim was in receipt of state benefits when the offence occurred.
Boulding, now of Everingham Road, Southey Green pleaded guilty to a count of fraud by false representation at an earlier hearing.
Defending, Rebecca Tanner, told the court that while it was difficult to quantify the total amount lost through Boulding's offending, the true 'loser' in the situation would most likely be the bank.
Ms Tanner told the court how Boulding's life had been blighted by his addiction to alcohol, and the recent gap in his offending was testament to his efforts to turn his life around.
In the weeks leading up to the sentencing hearing on April 27, Boulding, who appeared via video link from HMP Doncaster, had spent time in prison on remand, the court heard.
Judge Roger Thomas QC sentenced Boulding to an 18-month community order, the requirements of which include attending an alcohol treatment programme as well as a 20-day rehabilitation activity requirement.
"You are someone who has all manner of issues to conquer," said Judge Thomas, adding: "The first time someone experiences prison, is the time they are likely to learn a lesson - if it is possible to learn a lesson.
"With the short, sharp shock of prison behind you, I feel it is possible for me to impose a community order. You will have to do whatever the probation service want you to do."