How to save sketches in solidworks for old version users

Iges might be a good option, but press the "options" button when saving the file. There are additional settings you can enable when creating the file. I doubt one of them is clearly called "save sketches" or anything easy, but there might be an option to export curves which you could explore.

I don't know if it will work, but you might try saving the sketch as a library feature. maybe it will open in an older version? I've never tried to do so.

The sketch is pretty simple . Add a few dimensions, and it might just be easier to redraw it in the other version of SW.

YES it works by saving a 3D sketch in * .iges version 2017. Then open the file iges in 2016 ... (or older version) then convert each curve in a 3d sketch. It is interesting that we can destroy imported curves by removing the constraints of conversions of entities in the 3d sketch.
I have 2 versions 2016 and 2017 that are installed.

I would have made the same suggestions above, kudos to Fred. I researched the topic but do not have my laptop to confirm/deny that my suggestions work:

Could you save the sketch as a block and store it in the design library? Then log into the older version of solidworks, navigate to the same location, and grab the block?

Not sure if rerouting it through a path would allow older/newer version to open the same doc.

Or, maybe you could extrude the profile, upload it to grabCAD, download it in the older version of solidworks, and roll back the step?
Again, not sure if this will work 100%, I can try later this evening when i'm home.