Updating multiple rows with different values through foreach - Laravel Eloquent

I'm trying to retrieve multiple rows, loop with foreach, and update each of those rows with a specific value (based on switch)

I get the Method save does not exist error. Not sure what should be the syntax for this using Eloquent.

$appointmentreminders = Appointmentreminder::where('appointment_id', '=', $id)->get();

foreach ( $appointmentreminders as $appointmentreminder) 
{
           switch ($appointmentreminder->timeunit) {
               case "minute":
                   $reminder = clone($appointment->appointment_start);
                   $reminder->subMinutes($appointmentreminder->time);
                   break;

               case "hour":
                   $reminder = clone($appointment->appointment_start);
                   $reminder->subHours($appointmentreminder->time);
                   break;

               case "day":
                   $reminder = clone($appointment->appointment_start);
                   $reminder->subDays($appointmentreminder->time);
                   break;

               case "week":
                   $reminder = clone($appointment->appointment_start);
                   $reminder->subWeeks($appointmentreminder->time);
                   break;

               case "month":
                   $reminder = clone($appointment->appointment_start);
                   $reminder->subMonths($appointmentreminder->time);
                   break;
             }

             $appointmentreminders->reminder = $reminder;
             $appointmentreminders->save();
}

via Chebli Mohamed