I don't. Having been in the industry since the 1980s, I make little attempt to memorize the intricacies of whatever language my client is using. I know what I want to do and how I want to do it; Google can remember trivial things like syntax.
I don't know why I have that mental block, but I do. There have been some particularly notable cases in the reference book days where I could remember what page number to look at but not the syntactic construct on that page.
This is the "pass by reference" approach :^)
If you only use one language for a long time, though, don't you think you're better served by avoiding breaking for flow as much as possible?
I do a lot of Perl programming at work, and even after literally 10 years with it it still does, every once in a while, manage to surprise me. (This is, IMHO, a fairly damning criticism, but that's a well-beaten horse.) But I don't particularly have to think about the simple act of writing a single statement and haven't for a long time.
It seems to me there's a debate here going on about a total non-problem.
It's not every simple thing but there are some bits that for whatever reason manage to never stick in my head
I think the original question was about exams, which is an unnatural thing, and nothing to optimize a lifetime for. Write as much code as you can, study however is most effective for you, and empty your brain when you lay your pencil/keyboard down.
It's really useful to remember some things though like basic server configs to quickly make a site on a hackathon or some libraries for the languages you usually use if you're on a plane with no internet.
I write a lot of go, and it has a relatively easy syntax, but I constantly use my docs key binding to see what a function signature is or what the function even does. There's a lot of meaning behind "read the docs". I don't just do it once, I do it all day.