Windows shares via command line with user/pass, without mapping the drive? [closed]

It seems like you've missed an important part of net use before you ruled it out as a solution. You don't need to specify a drive letter with it.

net use \\server\share /user:test testpassword will work just fine. You don't need to specify a drive letter. This will allow access to that UNC path under the specified credentials.

Once you have the UNC path available under alternate credentials, you can launch an explorer session to the UNC path manually or by using start.exe as in start \\server\share.

A little two-liner as an example would be

net use \\server\share /user:test testpassword
start \\server\share