Algae that do not require sunlight and can obtain energy through utilizing sugars manufactured by plants are

Heterotrophs

Explanation:

Heterotrophs are organisms that are not able to form their own source of energy and are dependent on others to gain energy. Most of the algae are autotrophs which uses light energy to make organic energy source.  

Some algae are heterotrophs that do not require sunlight and pigments as they do not make their food on their own and utilize sugars manufactured by other plants and algae.  

They are also called colorless algae as they do not possess pigments. These heterotrophic algae are consumers, not producers. Therefore the correct answer is heterotrophs.