Can we upload google sheets api credentials on github?
You should never upload private/secret credentials to a public forum like GitHub.
There will always be people looking to exploit free credentials like that and it's impossible to know the damage that could be caused.  What if someone deletes data on your account? What if they spam calls and get your account suspended?  
The best practice is to put some kind of placeholder in the code that you put on GitHub and add a section to the ReadMe explaining where the credentials need to be provided.
I have made a web application that uses Google Sheets as a database. I want to upload my project on github. But since it uses google sheets API  for fetching data, I was wondering if is it safe to upload because I will also have to upload API credentials as well?
I have seen a lot of questions like this on Stack Overflow but none of them addressed this question clearly. Also, my application/database is nothing confidential or anything like that. My only concern is if uploading API credentials can cause any harm to my google account?