I'm going to call in sick 20 min before my shift at my first job
Why are you deciding to call in last minute?
Why not, I'm making some bank
I get that you get paid sick days but you shouldn't take advantage of your employer like that. Doing this will cause your employer to see you as unreliable.
I was only wondering how it would be to call in sick without a notice.
You should give ample notice if you have to call in sick. This will ensure that your employer can find someone to cover your shift.  By giving ample time, you will not be seen as unreliable at work.