SQL*Plus connection without using tnsnames.ora

No access to tnsnames.ora or just a temporary database and don't want to add the connection to the tnsnames.ora file?

Connect direct using this syntax (equivalent to the "Direct" tab in Toad):

sqlplus /@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=sdiora03.ont.local)(PORT=1521)))(CONNECT_DATA=(SERVER=DEDICATED)(SID=VENDORDEV))) as sysdba'