I only ever remember using one sick day--for any purpose--and I was legitimately sick. When I came in the next day the administrative assistant said "You sounded horrible on the phone!"
I wasn't even trying!
Sometimes my voice sounds worse the first thing in the morning, though.
People were implying that my body started to fall apart when I turned 40. Sick 3 times in 3 months sounded better than 4 times in 5 months.
I did need to work while sick in the Army. I hope that changed in the last year, too.