|From: Smithsonian's Lemelson Center|
"[...]Joseph B. Friedman was sitting at his brother's fountain parlor, the Varsity Sweet Shop, in the 1930s, watching his little daughter Judith fuss over a milkshake. She was drinking out of a paper straw, so we can be assured that the milkshake did not taste like grass. But since Stone's paper straw was designed to be straight, little Judith was struggling to drink it up. Friedman had an idea. As the Smithsonian's Lemelson Center explains, he brought a straw to his home, where he liked to tinker with inventions like 'lighted pencils' and other newfangled writing equipment. The straw would be a simple tinker. A screw and some string would do.
Friedman inserted a screw into the straw toward the top (see image). Then he wrapped dental floss around the paper, tracing grooves made by the inserted screw. Finally, he removed the screw, leaving a accordion-like ridge in the middle of the once-straight straw. Voila! he had created a straw that could bend around its grooves to reach a child's face over the edge of a glass. The modern bendy straw was born. [...]"
— Derek Thompson, The Atlantic