How to cite an ISO standard where I can only get access to the drafts?
It sounds like you're at a stage where it is somewhere between important and crucial for your project to have access to the actual standard: if the information you want to cite is in the standard, then that's the core document to cite, and if it didn't make it to the final version, then you may want to revise the text around the citation or even the research or code itself.

ISO standards are indeed not the easiest documents to get ahold of, but that's what libraries and librarians are for. Approach your institution's librarian and tell them that you need access to a document that's not in the library, and they will get it for you (that's their job!) either by purchasing the document for the library, if they consider it a good investment, or via inter-library loan. This can be a lengthy process, so you should approach them as soon as possible, but the upside is that if the standard's text does not change from the draft then all you need is a look at the full standard before you submit, to confirm that your provisional citation is appropriate.

In any case, even if you do get access to the full standard before you submit, I would encourage you to think of readers in your situation, who might have a hard time getting the standard, and I would thus recommend that you cite both the full standard and the working draft:


give the full standard as the main citation, but also
state that the same information is available in a working draft, and give it a separate citation that includes precise information on where it can be obtained.


As to how you actually cite it, that'll depend on the style guide you're following, but you can start with the format in this answer.

If you can't get a copy of the final standard, then it may or may not be appropriate to cite it as-is; for more on that, see Is it unethical to cite a paper or book that you have never looked at?. In that situation, it basically becomes a judgement call between the chance that the information won't be in the document you're citing versus the awkwardness of citing a working draft of a document that's since been Published, and we can't make that call for you.