In computer science, summer academic work usually narrows down to two avenues. On one side, grad students can go on to an industry (or research lab) internship where they can gain professional experience, as well as earn some extra money for the upcoming semesters. On the other side, grad students can spend the summer working on their research project(s) without any other academic or teaching responsibilities. Throughout my grad student career, I have experienced both and found each one to be uniquely rewarding. Previously, as a master student, I did a research-oriented internship where I had the opportunity to work on an interdisciplinary and industry-related research project. It was a great experience and I gained several skills which I would not have received any other way. Additionally, I was paid a decent amount of money, thus, I got some financial flexibility for the upcoming semester.
Nowadays, as a PhD student, I rather spend my summer working on my research projects than doing anything else. This strategy has proven to be quite beneficial as I am able to make substantial progress on my projects while still having some time to enjoy the summer.