Wud argue there is no substitute for sleep while travelling. Get as much whenever u can. Also keeps you from eating n drinking too much at wrong times in J..
The least affected trip (once on SQ but almost as good with EK) was midnight Mel departure, v little food/grog and thus some proper natural onight sleep. Felt ready to go again normally next morng in SIN, and a few hrs sleep on the long flt to Eu was enough to power me thru the anoon/eve on arrival, until a proper bed was again on offer.
But ppl are different - my wife sleeps less than I, and prefers anoon departures - she's happy to eat, watch movies n stay awake thru Sin, and then sleep once onboard the onight flt to Eu. Last time l tried that, I literally nodded off into the lakhsa after takeoff from Sin!
Melatonin seems to work, even the OTC stuff. Eye shade and ear plugs are also important to me. The number of times in the liminal zone of sleep when somebody turn on a reading light or clashes cutlery on china.. grrr
