undo clear out CACHE in terminal

Deleting files in terminal cannot be easily undone since it does not use the recycle bin. There is data recovery software that can restore files that were deleted from the filesystem but not yet overwritten by other data. However, I've never used such tools and cannot recommend anything in particular.

Why do you need to restore the cache? As far as I know, this folder isn't even backed up by Time Machine, so the data in it can't be very important and should be automatically rebuilt the next time apps are launched?

You have 2 choices.

A backup. Restore the files from a backup, if the backup has a copy, as many cache files are not backed up.

A file recovery utility, but the longer you actually use your Mac the more likely the storage will be reused.

And if you have an Apple SSD then it is too late for file recovery, as TRIM support will tell the SSD it can clear the contents of deleted files to make the block available to SSD writes. If you have a 3rd party SSD, and you enabled TRIM, same situation.