How can I get the raw query string from Laravel’s query builder BEFORE executing the query?

You can get it doing:

$query = DB::table('brands')
                ->join('products','a','=','c')
                ->whereNull('whatever');

echo $query->toSql();

But Laravel will not show you parameters in your query, because they are bound after preparation of the query.

So you can also do:

print_r( $query->getBindings() );