I like to alternate between "been throwing up all night" and "I have a bad migraine."
Throwing up all night is a good one, topped off with complaints of feeling weak because of it.
Best way to call in is to lay on your back or front with your head hanging off the edge of your bed. It changes your voice slightly when your phone in sick.
I ate too much chili yesterday, Boss. I can't make it in today and be able to work as I'll be in the bathroom all the time. Sorry !
I used to work for the public service where forms were required for everything, including sick leave. On one occasion I misspelt diarrhoea six different ways, crossed each one out neatly, and wrote in "stomach upset".
Another time I phoned in and said I had a touch of the collywobbles. And, so help me, the clerk asked me to spell it so he could write it down.
But the best, and most believable, excuse for a day off was not one of mine. If this video doesn't make you laugh I suggest you phone your boss and tell him you won't be coming to work next week because you're dead.
Way back when the Mrs. and I had a few, several children at home. I soon found that adults at work were deathly afraid of children's illnesses. L mentioned one day that the oldest one had a bad cough and suddenly I was alone. They feared catching hooping cough. Fortunately he didn't have it. So, I used the excuse, sparely over the years, I had caught "pink eye". You would of thought I had the Black Plague. "No don't take a day, take three". My favorite was, "It's Tuesday, take the rest of the week and see how you feel next Monday".