You need to explain more so you can get an answer.
How the user gets the product list in the first place if it is off line?
If the user is getting the product list from the Google sheet then as long as you can read from it then you can also write to the Google sheet.
It you know which row in the Google sheet to be updated then use this block.
This is an object containing the values of each column in that row to enable you reading the data of individual columns and save it to the table in Google sheet.
See this example of sorting a local DB but will show how to move data from one table to another. This example is using 2 localDB but the same is true when one localDB and the other is Google sheet.