catalinagoogle-drive
Sometimes the icon of Google Drive, on the top menu, disappears. This really annoys me also because this is happening always more frequently (and I don't want to go to the web browser and search for Google Drive, etc. I don't know how to solve this unless I restart the mac, but this is also annoying and undesirable.
So, is there a way of making that icon reappear, i.e. restart Google Drive's client on the mac, in case it dies?
I had to re-insall Google Drive upon El Capitan Upgrade. Make sure you have the latest version. For some reason it was not auto-upgrading for me.
Sadly, this is simply not possible in macOS. The Google Drive app, and now its successor Backup and Sync from Google, give the actual folder named "Google Drive" its custom icon in the conventional way, much the same way you could paste a custom icon on any other folder.
Unfortunately, all custom folder icons are ignored when displayed as Favorites in the Finder sidebar. You can confirm this by adding any folder with a custom icon to the sidebar. You can also show your home in List view to see that "Google Drive" does indeed have a custom icon optimized for that tiny display size. Finder is simply designed to ignore it, presumably to keep the Finder user interface as uniform as possible.
Best Answer
Just go to your Applications folder in Finder and double click the application "Backup and Sync from Google.app". If that does not work, other options may need to be explored.