Generally one 175ml serving will contain between a quarter-teaspoon and two teaspoons of sugar. This means splitting a bottle of wine over dinner - around two or three glasses - could contain around three teaspoons of sugar, which is two-thirds of a woman's recommended daily sugar intake.
Some sources claim that alcohol is converted into sugar by the liver. This is not true. Alcohol is converted to a number of intermediate substances (none of which is sugar), until it is eventually broken down to carbon dioxide and water. It's also often said that alcohol shuts down your body's fat-burning engine.