On a Google sheet, you can create both Linear Barcode and QR codes that you can use in Odoo.

Option 1: Linear barcode.

Use "Libre barcode 128" font or any other barcode font to generate a barcode from a text.

Option 2: QR codes

Use this formula to generate QR code:

=image("https://chart.googleapis.com/chart?chs=150x150&cht=qr&chl="&A1)

"A1" being the cell containing your text barcode.

Here is an example: https://docs.google.com/spreadsheets/d/1iZ8nMfyAmnD78cLKPwjZXnjz1lah9A33215xlw9oQk8/edit#gid=0