The drinking water in the morning, reactivating the alcohol in Pastis certainly works. I spent a couple of summers as a saissonaire in France 15 years ago with pastis/pernod being the drink of choice due to it usually costing about 1 euro. Typically you would water it down 5:1 but we used to do nearer 2:1 or less water. This led to a large volume in undissolved/un-absorbed alcohol in your stomach.
The effect of drinking a pint of water in the morning would dissolve this alcohol in you, allowing it into your system. It was the equivalent effect as a hair of the dog, just enough to take the edge off the hangover. This effect lasted just long enough for the ibruprofen to kick in.
We drank gallons of the stuff, but cruised through the summer hangover free (but vaguely pissed in the morning). Not ideal if you have to drive…