DJI said the update to the small drone's core software fixes some flight control issues suffered by the gadget.
The drone maker said it had warned owners about the deadline so they could avoid having their craft grounded.
But the mandatory update has caused some owners to question the control DJI retains over their devices.
In a statement, DJI said the update would improve how the Spark manages power. It also helps it work with smart spectacles that give owners an immersive view of what the drone films.
It added: "If the firmware of either the aircraft or the battery is not updated by September 1, Spark will not be able to take off."
The update is now available via the Go 4 management app used to configure and fly the craft as well as DJI's Assistant 2 desktop software.
A spokesman said it issued the warning so it could be sure Spark owners took the chance to update their drone before the deadline so craft are not grounded.
Gary Mortimer, writing on drone news site SUAS News, said DJI's demand that people apply the software had caused "consternation".
He said performance fixes bestowed by the software  were welcome but DJI's ability to throw a kill switch to stop the device working was more "questionable".
Earlier this month, the US Army banned serving soldiers from using DJI drones saying their use posed  "operational risks". In response, DJI drones were given a privacy mode that restricted who saw the video they shot.
DJI Spark drones will not fly after 1 September unless owners apply a mandatory software update, the device's maker has warned.