The last time I checked, most sugar is really dry (unless it's
something like brown sugar). So why is it categorized as "wet"?
Sugar is not really a wet ingredient, it's just treated as one
in certain types of baking (i.e. cakes). When making a cake or
other "fluffy" baked good, you want a fairly small amount of
gluten to be produced, otherwise you'll get a chewy texture
instead, and you definitely don't want a cake to be chewy like
bread. Dissolving sugar in the water inhibits the gluten-forming
proteins. It's a method (actually, the method) of adding more
liquid to the mix without getting a tough, chewy cake. It is for
this reason that sugar is considered a "wet ingredient" -
because the process only works properly if you add it with the
water, not with the other dry ingredients. It's even possible
for sugar to be a dry and wet ingredient in the same recipe; you
might add just enough sugar to the water to get the right
texture, and add more to the dry ingredients for further
sweetening. I'm not sure what th