Is it because expressions of quantity often mean "[quantity] of something"?
Also, I thought the genitive here was because of potrzebować. Once again the comment section proves useful, so thank you. :D
Would "wody" without "troche" (sorry, I can't do the accent on my keyboard) be sufficient to communicate the idea of "some"? I may be confusing it with Russian, but I thought genitive could also be used partitively to communicate the idea of "some."
Some doew not express the idea of a small amount I believe troche means. A drop or a little would be better
I think it works well, "trochę" is just some unspecified amount, true, probably small, but still. "a little" works. "a drop", even though I understand that's not literally a single drop, sounds rather like a very small amount...