I like to use honey, cane sugar, and brown sugar. I carmalize the brown and cane sugar, then add the honey and mollasses until it thickens. Then I heat up 1 litters of water to 115 F, then add 4 tbsp of the syrup to the water, retemp it and add cold water till its 115 F again, add yeast and start the fermentation while the syrup cools to a yeast safe temp, add the vanilla bean or extract to the syrup while it cools. Then I add the syrup and shack the hell out of it till its all mixed.
Since you fermented the yeast in a 115 F environment it will ferment 4-5 times faster, it will pressurize in about 10 hours rather than 24 or even 48. I see alot of recipes that don't seem to be very friendly with the yeast. Main things when dealing with yeast is to provide a sterile, warm(115 F ideally), with some kind of carbohydrate(sugar is a simple carb that breaks down quick). After that refrigerate it till you need a cold one.
In my recipe I get a sort of thick syrupy beverage, however not too thick, with a brown tint and a deep rich flavor. This isn't the modern day clear cream soda, but the old fashion kind.