Regardless of which sleeping pill you take, it is better to skip dinner on board for at least two reasons. Number one, the pill itself is more effective on an empty stomach. Second, by the time you eat your meal you will have lost, at a minimum, one to 1.5 valuable hours of sleep. Especially on an eastbound flight, it is also advisable to eat dinner before the flight anyway because of the corresponding dinner time in your destination time zone. So grab some food in the terminal or at some time prior to your longhaul flight and use the flight to get as much shuteye as possible.