hmmmm.... If you are on windows machine try to edit
%systemroot%\system32\drivers\etc\hosts
Be sure to have admin rights to edit this file. Append next line in the end of file, change ip to ip of clients web server where site is located.
192.168.50.110 www.foo.com
If this not working you have to check "Default gateway" settings on your machine. Like you can try to enable "Use remote gateway" on network interface which VPN creates,, to go through clients network.