He had placed the bombs throughout Christchurch and a man needed two hearing aids after suffering hearing damage when one bottle exploded.
He told the court he wanted to apologise to the court and community.
"It was a foolish, insensitive act, and I regret it – I really do."
Coombs' lawyer said his cleint had been watching prank videos on YouTube before he recorded footage of himself pretending to cough on fellow shoppers at the Barrington Fresh Choice.
Judge Jane McMeeken said he owed the country an apology, describing the incident as serious – and this wasn't an isolated incident.
McMeeken said that on March 31, he uploaded a very serious video where he pretended he had the virus – and told viewers how awful it was.
"At the time you behaved in this appalling fashion, you had no way of knowing whether you really had the virus," the judge said.
"This is an unprecedented time in New Zealand's history … many people are suffering.
"Your behaviour would've added to that suffering.
"It's vitally important to our country we get out of lockdown as soon as possible. Your actions could've stopped that."
He sparked outrage over the weekend when he filmed himself coughing and sneezing on customers in the Barrington Fresh Choice and posted it on Facebook.