The court was told the video allegedly showed Mir removing the trainee's bottle before putting it back soon afterwards.
Prosecutor Andrew Baker alleged the stunt was a "form of retribution" done to show "the risks of what could happen" — although he also claimed there was "animosity" between the pair.
"His actions were at the very least foolish and, we would say, criminal. His intention was to annoy her at the very least," Baker said.
"Whether it was some form of retribution or to teach her a lesson, it was an incredibly stupid and criminal thing to do."
According to the BBC, Mir told the jury he wanted to "shock" his colleague, but he never planed on her actually drinking it.
Instead, he claims he intended to warn her first but became too busy with customers.
"My intention was to remove the bottle. I regret doing what I did," the BBC reported Mir as saying.
"It was a moment of madness.
"I was trying to shock her. But in hindsight I have caused her distress. I am sorry to her."
Mir said he and Abdulquader had a good relationship, and he has denied a charge of causing a noxious thing to be taken with intent to annoy.
However, the trainee told the jury she was struck down by vomiting and diarrhoea even after spitting out the drink.
A pharmacist and former colleague of Mir told the court the rule banning drinks on the dispensary floor was well known and was designed to keep people safe.
"It is a very well-known rule and there used to be posters. It is for a variety of reasons, hygiene being one of them. There may be an instance when a colleague might slip on the floor," Birmingham Live reported the pharmacist as saying.
The trial continues.