A plastic door handle for the win
When you stop and think about it, any method will succeed in opening a door. This essentially confirms that, like a molded plastic piece with some screws, there is a makeshift door handle that should do the job just fine.
Sure, it doesn’t appear the greatest, but for a door that you don’t care about how it looks, this will take care of everything. They even have a hole drilled if they want to add a deadbolt. That’s clever.