Shaun Dunn had been warned about his behaviour by the driver as the bus headed north on the motorway through Dumfriesshire, and was told he would be put off at the next available stop.
But he then confronted the driver and passengers with the syringe shouting that no one was going to put him off.
On Tuesday, the court at Dumfries was told that he eventually left the bus himself when it stopped at the services station at Johnstonebridge.
In the dock, Dunn, 30, from Dundee, admitted assaulting the driver and threatening passengers on the bus between Manchester and Glasgow and also behaving in a threatening or abusive manner and shouting and swearing at the passengers.
It was stated that earlier passengers had complained about Dunn’s erratic behaviour interrupting conversations and apparently under the influence of some substance.
A solicitor admitted that Dunn had 39 previous convictions, but more than half of them involved dishonesty.
He had had a problem with drugs and had been on methadone but relapsed into the use of illicit substances resulting in his behaviour.
Sheriff Brian Mohan said the events must have been extremely alarming for the passengers and jailed Dunn for 12 months.