Apart from being ugly people use the and/or construction ambiguously. Its precise meaning is often unclear.
Good writers avoid unclear writing.
Writers reach for the term when they mean either and or or, but not both. In this case it is better to just use the one you mean.
If you do mean “either and or or or both” then spelling out your meaning in full is unambiguous:
You can eat an apple or an orange, or both.
And/or crept into common use from the legal world, where it is widely used as a catch-all, but is still controversial in some circles as the meaning is imprecise.
The same applies to using a slash between words. It means or, so don’t be lazy and leave your readers to guess your meaning.
Be precise, use the word. It is only two letters.