One technique I utilize is to redirect output to an ASCII file using the Out-File cmdlet.
For example, I often run SQL scripts that create another SQL script to execute in Oracle. With simple redirection (">"), the output will be in UTF-16 which is not recognized by SQLPlus. To work around this:
sqlplus -s / as sysdba "@create_sql_script.sql" |
Out-File -FilePath new_script.sql -Encoding ASCII -Force
The generated script can then be executed via another SQLPlus session without any Unicode worries:
sqlplus / as sysdba "@new_script.sql" |
tee new_script.log