how is it associated with sugarcane?
They have been cultivated in tropical climates in the Indian subcontinent and Southeast Asia over centuries for the sucrose found in their stems.
Sugar
They have been cultivated in tropical climates in the Indian subcontinent and Southeast Asia over centuries for the sucrose found in their stems. 
where does the sugar in fruit come from Fructose where did it get its name from? Sanskrit ("śarkarā"), meaning "ground or candied sugar", came Persian "shakar". does it cause tooth decay? Yes, in 2003 WHO report stated that "Sugars are undoubtedly the most important dietary factor in the development of dental caries". how is it obtained? They are common in fruits and vegetables.
wiki:19674675
Sugar [SEP] Sugarcane
Global production of sugarcane in 2016 was 1.9 billion tonnes, with Brazil producing 41% of the world total and India 18% (table). Sugarcane refers to any of several species, or their hybrids, of giant grasses in the genus "Saccharum" in the family Poaceae. They have been cultivated in tropical climates in the Indian subcontinent and Southeast Asia over centuries for the sucrose found in their stems. A great expansion in sugarcane production took place in the 18th century with the establishment of slave plantations in the Americas. The use of slavery for the labor-intensive process resulted in sugar production, enabling prices cheap enough for most people to buy.