Newcastle-based Out of the Kitchen had denied the unauthorised sale of nitrous oxide, also known as "laughing gas", through its Toon Whip brand.
Although it is used legally in the catering industry, it can be fatal when used as a drug.
The case followed an undercover investigation by the BBC in which a reporter was sold two canisters.
Toon Whip advertised a "whipped cream delivery service", but the reporter was given instructions by the firm's staff on how to inhale the gas using a balloon.
Newcastle Magistrates' Court heard Out of the Kitchen Limited made a profit of £40,000 in 2015-16, with £10,000 of that figure coming from Toon Whip.
The fine must be paid within 14 days.
Directors Jonathan Lawrence, 30, of Stamford, and David Jenkins, 29, of Newcastle, are also charged with the unauthorised sale of nitrous oxide.
They have entered not guilty pleas.
The case against them was adjourned until 23 January.

24 July 2017 Last updated at 14:56 BST
He's been racing sharks... Yes, you read that right.
Michael Phelps had a special shark suit to help him compete against the ocean predator.
And don't worry - he actually wasn't in the water with them, it was done with special effects.
Watch this to see who was the fastest...
Pictures courtesy of Discovery
A catering firm has been fined £7,620 for selling gas used as a recreational drug.
[NEXT_CONCEPT]
Olympic superhero Michael Phelps is one of the fastest swimmers on Earth, but he's been taking up a pretty weird challenge.