Connect to SQL Server database from multiple international sites

Question

Hi,
I need to investigate which ways are possible for a company A to connect to a SQL Server database from multiple company sites A1, A2, A3 ... in different countries and be able to make changes to the database through an interface from Visual Studio for example. I know there's something like VPN, but I was wondering if there would be other good options, so I can investigate all options, the prices and pro and cons from all of these.

Thank you, much appreciated.