All right, I'm tired of people saying that adding some type of sugar (be it cane, corn, whatever) is going to make it taste like Cider. I would even bet that most people have never tried doing this and are just hopping on this anti-sugar bandwagon because it's the "in" thing to do.
If you carefully balance your recipe, pitch the necessary amount of healthy
yeast, and control your fermentation temperatures (all three which you should be doing anyway), adding sugar to your beer will NOT
result in it tasting "cidery."
I hypothesize this rumor started from poorly crafted "kit" beers. These kits call for cane or corn sugar as a substantial amount of fermentables - more than would normally be called for. This then evolved into an "all sugar is bad" and this whole "cider" BS. This reasoning is also most likely augmented by the fact that these kits did not contain the best ingredients (extracts and yeasts) or instructions for their use. I would also venture a guess that because these kits were geared for the new brewer, fermentation temperatures were probably uncontrolled, resulting in hot fermentations and fusel alcohol warmth that made an unpalatable beer.
Adding sugar to your recipe can be advantageous in that it helps "dry" out the beer and thus reducing cloying body sweetness in some styles and accentuating hop bitterness in others. If making or using dark candi sugar, you may also be adding flavor and color components to your beer.
There is extensive documentation on the internet from fantastic brewers such as Jamil Zainasheff who have used amounts such as 3 lbs of regular cane sugar
in a 6 gallon recipe that has placed in the second round of the National Homebrew Competition. I am not trying to be a Jamil fanboy, I am merely stating that you don't take home gold medals with beer that tastes "cidery" (Source: The Jamil Show, Belgian Golden Strong
There is also the advantage of using simple sugars in high gravity fermentations in order to make them attenuate properly. In this case of extreme fermentations (I would estimate around the 1.100+ area) it is best to "step" your fermentations. For example, allow the yeast (don't forget that healthy pitch!) to consume the maltose-based sugars first and then when the gravity has dropped, start dosing with the simple sugars. The point of not adding all the fermentables at first is because it will overwhelm the yeast due to viscosity of the wort and because the yeast will choose to metabolise the simple sugars (glucose, sucrose, fructose) in preference over the maltose. These latter sugars (which come from the malts) will be left unfermented, resulting in cloying sweetness and a heavy body.
(Source: Sean Paxton's Dogfish Head 120 minute IPA clone recipe
As mentioned, hoppy beers may benefit from simple sugar additions to dry out the malt backbone, leaving the hop characteristics (bitterness, flavor, and aroma) more pronounced. Again, you want to make sure of balance in the recipe (you still want malt!), but you don't want all those expensive hops covered up by residual sweetness or body that may not mesh well. Make the most of the hops during this time of record prices by getting your beer to ferment drier, leaving a pleasant hop tone to the beer.
(Source: 2008 Samuel Adams Longshot Winner: Mike McDole's Double IPA, aka Pliny the Elder clone
Don't be duped: sugar has its place in beer by making it more digestible and easy drinking, when used with a solid and balanced recipe.