English. People from the countries you mention will have spent a great deal of time learning it in order to work in an international team.
I suspect, though, that you already speak English, perhaps as a native language. Either way, I commend you for choosing to learn an additional language. The world needs more people like you.
I would suggest that it really depends on which specialism you want to go into, your own interests, and what you would like to achieve in your career.
For electrical engineering with a focus on chip design and embedded systems or robotics, Japanese might be an interesting line to pursue (you’d also have an advantage in that you’ll find it far easier to learn the written form of Japanese if you already know hanzi). For mechanical engineering, Hindi or German would be useful. For aviation engineering, You might learn French and go to work for Dassault. For petrochemical engineering, you might want to learn Arabic (working in the Middle East is also a very good way to make lots of money).
The question is, then: what do you want to do?