None of the methods mentioned will clean the sharpie mark to non existent. Some may remove the top layer of the sharpie but you can never remove the underlying color, you will always still see it. I have tried everything mentioned including magic eraser, soap and water, an actual golf ball cleaner, acetone, gasoline, hand sanitizer, rubbing alcohol, goo gone, finger nail polish remover, NOTHING works so you are basically stuck with the faint outline of whatever was put on the ball. If someone has a foolproof way to put the ball back to completely white and no faint outline, I haven't been able to figure it out yet, I'm all ears.

I tried using white permanent marker. Worked great.

Use white permanent marker on top of original mark!

Might sound daft but try spraying some deodorant on it!

I use a dry erase marker to cover the mark then wipe both away.

Make them practice balls, or game them when you are playing as a single. If they are all marked different easy to tell ball A from ball B