For instance, the command
-D username=guest -D "password="
authorization failed: Could not authenticate to server: rejected Basic challenge (https://svn.dev.java.net)
because the issued cmd line is
cmd.exe /X /C "svn --username guest --non-interactive checkout https://...
cmd.exe /X /C "svn --username guest --password "" --non-interactive checkout https://...
i.e. the empty password is not propagated to the server, making the auth challenge fail.
Note: To reproduce this issue, the svn client's auth cache in auth/svn.simple must be empty. Otherwise, a the cached auth data from a successful login will shadow the issue.