To understand the difference, you simply have to look at the ingredients. By definition, pure juice should only contain juice (100%), whether or not it’s made from concentrate. For certain juices, legislation permits the adding of vitamin C and sugar. In such cases, we’re obliged to mention these inclusions on the label.
If juice is not the product’s only ingredient, it’s then considered a cocktail (i.e. it contains from 0% to 99% juice). Therefore, it depends on the position of the word "juice" within the list of ingredients whether the cocktail has high juice content (at least 50% juice) or not. For example, Oasis Health Break cocktails have a high juice content. If the juice is listed after the sugars, its percentage can vary between 1% and 25%.
If there’s no mention of the word "juice" in the ingredients, the product is considered a drink. Drinks are composed of water, sugar, fruit flavours and colouring.