There's a lot of factors - when I was in a job I liked and wanted a good reference, I'd be apologetic, do it as far in advance as I could (the evening before is better than the morning of), let them know when I'd definitely be back at work.

When I worked at Amazon, the policy is very specific, the company is massive, I didnt care about getting fired, and most of my co workers weren't fluent in English, so I just said 'hello, I am ill, I cannot come to work, I am using PTO/NPTO, thanks.'

It also depends if you're expected to find cover or if they are.

If you 'never' do it, then you've probably got a reputation for being reliable, and as such you can take a day off guilt free. I'd say:

Hello (person),

I have come down with an illness and I am feeling too sick right now to work today/tomorrow. Apologies for the last second notification - it came out of nowhere.

I am confident it will pass and I will be available to work for (next shift/whatever), if this changes I will let you know as soon as possible. Apologies for any inconveniences.

Many thanks, From PERSON.

You could even add a grovelling 'you know I don't call in sick often' sort of remark.

If anyone ever asked me in person what I had I'd just say 'oh the works I don't know just totally knocked out yeah very weird anyway'