SQL Server renaming table from another database
You should use dynamic sql to do this. Build a string and execute it. As long as you know the name of the destination database, everything should be fine.

use CurrentDB
declare @x varchar(1000), @otherDb sysname = 'NewDB';

set @x = 'use ' + @otherDB + '

EXEC sp_rename ''dbo.temp'', ''temp2''
'
exec (@x);
print @x;
GO