The fourth bottle of vanilla cream soda turned out pretty good. There's still a hint of yeast, but it's way in the background and probably unavoidable with this carbonation method. Compared to a commercial cream soda (Wildwood from Kwik Trip) it's still not as flavorful and is not nearly as sweet. The Wildwood is 120 Calories per 8 fluid ounces. Mine is 45. The next bottle will have yet more flavoring, and have the sweetness boosted with Splenda. This reminds me of something I heard at Penguicon. At least one of the people who mixed up the syrup for OpenCola wouldn't drink it or at least not very much of it, having seen the huge amount of sugar that goes into it.
The small bottle of anise flavored soda sort of worked out. Predictably, any yeast note was drowned by the anise and I figure I can cut back on the amount the flavoring. (jmaynard says I need to cut it back to zero as he claims including any just makes "yuck soda.") The carbonation seemed a bit weak, perhaps more time was needed as I cut everything in half for the lowered volume and perhaps the time needed to double.
I also tried making ginger ale. This worked, though it either needs a bit more ginger, or I need to find a finer cutting grater. It's decidedly ginger ale, just not quite ginger enough. Also, the warnings about keeping a closer eye on ginger ale than other sodas is true. Yeast loves something in ginger and the pressure builds fast. A day or maybe a day and a half is plenty for ginger ale while three or four days are needed for everything else.
And I really need to be patient and only do one bottle at a time or per week or such. Even cutting back on the sugar, I don't need more than one bottle of fizzy sugar water around at any given time.