What should an Indian CS student do in his sophomore year?

Explore. Explore like crazy.

Try everything:

• Web development: Django Girls Tutorial. Learn the basics of how web applications work. Understand the client-server architecture.
• Mobile app development: Android Courses | Udacity. Learn how mobile devices are different from desktop devices. Learn about REST APIs
• Machine Learning: Machine Learning | Coursera. Learn how Machine Learning algorithms work. Take up simple ML-based projects.
• Cryptography: Cryptography Courses | Coursera. Learn how your data is ensured to be secure when it is transmitted across machines.
• Competitive programming: Sphere Online Judge (SPOJ). Learn to build the right programmer attitude.
• Research: (I am not the best research guy).
• …

Basically, explore all avenues of Computer Science and figure out what interests you the most. This way, you can plan your course-work, projects, and internships accordingly. For instance, if you have decided that you want to build a career in Machine Learning, you can aim for an internship at an ML-based company/startup during your 2nd/3rd year summers.