How Sketch took over 200GB of our MacBooks
Thomas Degry

This problem is easy to fix for a sketch file.

While viewing your file in sketch, go to File > Revert To > Browse All Versions…

In the screen where you compare current and old versions, mouse over the top of the screen to get the menu bar again.

Then go to File > Revert To > Delete This Version…

To delete all previous versions, hold the option key. The menu should now read:

File > Revert To > Delete Old Versions…

You can delete a specific version way or delete all old versions within Sketch. No terminal hacks or anything