This is the drink that James Bond orders for Rene Mathis when the latter introduces him to Vesper Lynd in Casino Royale.
This drink – just cognac (or Brandy) with water – is a simple drink which was once very popular:
The most popular way to drink Cognac used to be the “Fine à l’eau” until World War II. Take a measure of Pierre de Segonzac Prestige, pour in 3 measures of pure water and that’s it : contrary to a popular belief, water gives you the chance to appreciate aromas during the first ten minutes.
You can also use sparkling water as well. A brandy and soda is a fairly frequently ordered drink in the Bond novels.
Later, in From A View To A Kill, Bond is sitting outdoors at a French café pondering his libation options, lamenting that outdoors on pavement is not a place for serious liquor like vodka, whisky or gin. He considers other options, including the fine a l’eau.
A fine a l’eau is fairly serious, but it intoxicates without tasting very good.
Makes you wonder why he ordered the drink for Mathis if this was his opinion of it.