Your question has a broad scope. Yet, I'll try to give a simple answer. Basically, naturally occurring sugars or sugars contained within unprocessed foods including vegetables and fruits are considered intrinsic sugars. Examples for the most common intrinsic sugars are glucose, fructose, lactose, and sucrose. Besides them, other minor amount of natural sugars in foods such as galactose and maltose are also considered intrinsic.
The other type of sugar (e.g., the sugar in a juice) is called extrinsic sugars. Extrinsic sugars include processed sugars or sugars that are added to food. Extrinsic sugars include syrups such as honey, added sugars in soft drinks, and artificial sweeteners. However, there is no clear difference between intrinsic versus extrinsic sugars (Ref.1):
Development of caries in man is associated with dietary sugars, but the relationship between sugar contents of individual foods and their cariogenic potential is unclear. A recent report categorized dietary sugars as intrinsic (mainly fruit and vegetable) and extrinsic (mainly added sugars, milk, and fruit juices) and concluded that consumption of extrinsic sugars (except milk) should be replaced with that of intrinsic sugars. This paper examines briefly the dental consequences of the recommendations.
Yet, Live Strong recommends following:
According to the American Heart Association, intrinsic sugars should be limited to at least half of your daily intake of carbohydrates and extrinsic sugars should be limited to no more then half of your maximum daily amount.
- W. M. Edgar, "Extrinsic and Intrinsic Sugars: A Review of Recent UK Recommendations on Diet and Caries," Caries Research 1993, 27(suppl l), 64-67 (https://doi.org/10.1159/000261605).