How to update remote branches using Visual Studio Git?

You may have to save settings in your Visual Studio "Team Explorer" to always prune on fetch (then fetch branches again from a remote server), to do that follow these steps:

1. Click on "Team Explorer" Window in your Visual Studio
2. Then Click on "settings"
3. Now from the Menu Options Select "Global Settings"
4. In the Global settings window, Set "Prune remote branches during fetch" to "True"
5. Click "Update".
   
6. Once you have followed the above steps, open solution in Visual Studio, click "Team Explorer"-> Select "Sync"-> Select "Fetch" in synchronization tab.

You should now see updated remote branches now.

OR

In your local repository directory, you should use git fetch -p (or git fetch --prune) command, it will check if the tracking references of branches, exist or not and delete non-existing ones before fetching.

Open Team Explorer in Visual Studio, select the branch which you want to update and then click on "Fetch".

OR

If you don't have remote branch selected or locally, checked out, Find the remote branch in remotes -> origin, then double-click that branch to get it selected locally. Now you can fetch/sync/etc.