Sugar is a carbohydrate, There are different form of carbohydrates. Sugar is a simple carbohydrate. We need carbohydrates because they give us energy. In short, carbohydrates give is energy.
We get energy from foods such as rice and pasta, potatoes etc. the reason for this is, in simple terms, the body turn starch into sugar. When athletes etc eat pasta they are doing it to produce sugar and therefore energy. This source of energy is slow releasing so does not, in general but can, cause energy spikes.
However, normally active people will burn this energy without having a spike so it is down to general behaviour. See comments below for more info.
As Sean says, complex carbohydrates (like rice, pasta, bread and potatoes) have to be broken down into sugars by your body. This process takes time, so the release of sugar into your system is relatively slow – no hyperness. When you have sugar (in it’s simple form), this is swiftly followed by a spike of it in your blood. It can make you feel energetic and sometimes nervous – hyperness. Beware the low that follows the high, though…