My preferred recipe for a good syrup is the one that comes from A Mountain of Crushed Ice:
There are many varietes of edible passionfruits, they are flowering wines growing in the tropics and temperate areas and the flowers are very beautiful. There seems to be very different tasting commercial passionfruit juices and syrups and so the amount of other sweeteners needs to be adjusted to what you got. Here we have sweet passionfruit juices and a quite tasty syrup called BarKing which is made in Sweden. I`m usually not a fan of commercial ingredients but this one is tasty (in small amounts), and has the ability to transform a drink into cup full of godness.