Question

Why sugar and salt assumes the shape of the container despite being a solid?

Answer 1

When sugar and common salt are kept in different jars, they take the shape of the jars, still they are considered as solid .
Reason:
--->As, solids are rigid form of matter and have  fixed  shape and volume.---->even though , common salt and sugar crystals when poured in any container, they take the shape of container, still each granule of common salt and sugar retain their fixed shape and volume .
Conclusion:Hence they are considered as Solids. 

Answer 2

it may seem that sugar and salt does not have fixed shape but if we take an individual particles of salt or sugar it has a fixed shape.
so salt and sugar is known as solid.

hope it helps you.