I have a Google spreadsheet that has not been made public, but just available to anyone that has the access link. Though I can access the data in CSV format from my browser
To access other tabs you need to click and get the gid of that tab, so:
https://docs.google.com/spreadsheets/d/1GxmL3bbejjGx-Ji7kzsnZLzkSaMrfX5WwgRAvvqfqpw/pubhtml?widget=true&%3Bheaders=false#gid=2120833204
Becomes:
https://docs.google.com/spreadsheets/d/1GxmL3bbejjGx-Ji7kzsnZLzkSaMrfX5WwgRAvvqfqpw/export?format=csv&id=1GxmL3bbejjGx-Ji7kzsnZLzkSaMrfX5WwgRAvvqfqpw&gid=2120833204