If you are an underclassman with little or no direct work experience, there are still other methods to stand out when applying for internships, such as: 

1. Extracurricular activities: Joining clubs or organizations related to your field of interest can help you gain valuable experience and demonstrate your passion. Clubs such as marketing, debate, robotics, investment, and engineering. As a plus, you can take on leadership roles in these groups you join to demonstrate your leadership skills. 
2. Courses and workshops can help you develop technical skills, such as programming (C++, Java, SQL) or data analysis, as well as soft skills, such as communication and teamwork. 
3. Even if it's not directly related to your field of interest, gaining experience through volunteering or part-time opportunities shows initiative and willingness to learn. Remember that there are a lot of transferable skills you gain from such experiences. 
4. Remember, you can always highlight school projects during your interview! School projects are still valid experiences that can highlight many valuable aspects that companies look for in candidates such as how you work on a team, handle challenges, and problem solving skills.