You can easily attach a spreadsheet to an email (just as you would a photo or other kind of file) and send it. So long as it's unprotected, the recipient could edit it just as you would. In a case like that, the other person would have to send it back to you after making whatever changes he or she wanted to do
A little bit more tricky would be to place the file in OneDrive or GoogleDrive, sending a link to the file, a link that grants edit access. That would become a "shared file" which anybody with access to it could edit.