Why isn't my sugar dissolved?

It's yeast. Sugar doesn't float, dissolved or not.

Sugar dissolves easiest in a hot liquid - you'll probably need to stir it but it should dissolve VERY easily. Sugar doesn't float though, undissolved sugar would sink to the bottom of the bottle.

Yeast doesn't "carbonate" a drink, it's the reaction between the yeast and the sugar that causes carbination - the yeast "uses" the sugar and produces carbon dioxide and alcohol as waste products.

Air is needed to allow the yeast to start working and I'd expect it to take longer than a couple of days to even begin fermenting.

Are you sure it's sugar?

Undissolved sugar won't be floating
at the most it will be like a sludge on the bottom.

sugar doesn't float...are you sure thats what you are finding in your root beer?

sugar should have been stirred til it dissolved in the liquid before adding the yeast. Are you sure it isn't the yeast remnents that is floating in your drink? You need to pour the root beer so as not to disturb the sediment in the bottom of the carafe! that last bit should be tossed out. No, the yeast never completely dissolves in any home made sodas whatever the flavor. I make Ginger Beer and always toss about 1/4 cup because it has yeast bits in it. They do not taste nice. But it is not the sugar!

Sorry, sugar +yeast +water = alcohol +CO2

Next time, disolve it in hot, ( boiling water )........then cool it to a usable temp

did you try heating it first? before you added the yeast

Heat it up.

sounds like that you took the beer out to early

You need to add your priming to a bottling bucket and do it as a batch rather than in each bottle.

Use treacle

Very hot water should dissolve it BUT the amount of sugar that will dissolve in a specific quantity of water is limited. After water is saturated with dissolved sugar, additional sugar will just sit sink to the bottom and not dissolve.

Use syrup

Too much sugar.

Tru another batch so

use granulated sugar...easy dissolve without warm water

Dissolve it in an equal part of hot water before you add it next time. For this case, if you de-gass, it will most likely dissolve, and then you can re-carbonate with bottle fermentation.

Sugar dissolves best if it is melted in warm/hot liquid. Even a cup of liquid can help speed up dissolving several cups of sugar.
Since I have never made soda I have no idea how you can dissolve it at this point. Unless there is a way to warm it up.

you need to stir to make it dissolve