Methanol will not be an issue, just try it, if it is horrible then bin it. Costs nothing...
Personally I would use VG (Vegetable Glycerine) based flavours as some people can have reactions to PG (Propylene Glycol) when vaped, but don't know about them when consumed plus the fact it will be so dilute may not even matter.
I might give this a go with forced carbonation as I already have the kit and flavours, Thanks.
methanol is ALWAYS produced by fermentation.
At ABV's under 20 percent or so it is not an issue, only when you are distilling does methanol become an issue, as the distillation process concentrates the alcohol (by removing the water from the solution) so you will be increasing the methanol content for every mouthful. that is why they talk about heads, hearts and tails in distilling.
A glass of wine contains about 0.0041 to 0.02 percent of methanol by volume. The same glass will have about 10-15 percent ethanol. Methanol is much sweeter than ethanol, and even a small amount adds flavor. This sweetness is what makes methanol attractive to use in an artificial sweetener.
Most people regularly consume up to 10 mg of methanol per day as part of their normal diet.