It seems that I'm in a similar position to you, CookieGhoul. I'm from the UK and hoping to study physics at ETH. I don't know of any courses run by the university themselves but there are other courses you can go on to improve your German. In case you didn't know, to be admitted to ETH, you need a qualification in German; level C1 with passes at "good" or better in every part of the exam.The C1 level exam seems pretty hard so don't underestimate the amount of work you'll have to put in; having said that, it's almost certainly an achievable target. If you can spend some time in Germany, you'll probably find that it helps your German a lot, I intend to do something along those lines this summer.
dadude, is German your native language or did you need to learn it before going to ETH?