Here is how you can prevent it from copying, download, or printing:

  1. Open your Google Sheet
  2. Click on a green Share button in the top left corner. Share with people and groups window should appear.
  3. Click on the Settings gear icon in the top left corner of the Share with people, and groups window.
  4. Disable checkbox: Viewers and commenters can see the option to download, print and copy
  5. Wait once your settings will be updated. You should see an notification
  6. Click Back
  7. Click Done

Once you will do it people can't copy your Sheet, at least in an easy way.

Important to know: Since your Google Sheet is public they can still see your Google Sheet and copy each cell one by one. This is hard and requires some time to do it, but still possible.