Wine charms are great, but there's there are two problems with them: first, they generally don't celebrate the world's most fun transcendental number. Second, they don't work for plastic cups -- and if you're having a rockin' Pi Day party you probably won't be busting out the glassware. So I decided to make some π-themed beer charms at TechShop.
The key things I wanted in a beer charm was that it would fit around the lip of a plastic cup and stay there, and that it had some room to write your name on it.
I started in Illustrator and found a font that had the profile I was looking for: Stencil Std - it is curly, with one π leg thicker than the other (giving space to write a name). The legs have to change, however: the should be bend inwards to grip the wall of the cup.
Starting with a 1" x 1" artboard, draw a π and scale it to fit the artboard. Next, turn the text into an outline with Text > Create Outlines.
To rearrange the legs (which sounds like something a mobster would do), you'll have to cut the path: Carefully draw a line across the corners of the leg that you want to cut, then use Object > Path > Divide Objects Below.
Finally, rotate each leg inwards until it creates a pinch at the bottom and leaves a gap at the top, for the cup rim. The only way I found this to get exactly right is to test out each change with a real charm until it works for the cups you have.