Buy a brand you know you can trust and be certain the package is clean, dry and has no insect infestation. There's very little that can go wrong with it. Granulated Sugar Granulated sugar does not spoil, but if it gets damp it will likely cake up or get lumpy. If it does, it can simply be pulverized again until it regains its granulated texture. Granulated sugar can be found in varying textures, coarser or finer.
All names refer to the same kind of sugar, that is white granulated sugar very finely ground.
For commercial use there is a range of textures from coarse to ultra-fine. Not all manufacturers will indicate the grind on the package though. Sugar refiners usually add a small amount of corn starch to prevent caking. Powdered sugar is as inert as granulated sugar, but it is even more hygroscopic and will absorb any moisture present. If it absorbs more than a little it may cake up and get hard.