BuzzFeed editor Jenae Sitzes utilizes this defense with her own cats:
“I decided to finally give these cord protectors a go recently and can absolutely vouch for their effectiveness. One of my cats, Sneaky, is a notorious cord chewer and particularly loves going to town on the charging cable for his automatic water fountain — you can check out the damage above. I was getting to the point where I was afraid it’d stop working entirely, so I ordered these protectors in the 1/2-inch size. They snap on and off *so* easily — flexible enough for removal, but thick and durable enough that your kitty’s teeth are no match against the thick wire loom. Sneaky pretty quickly realized he’d finally been defeated once he discovered these on his favorite chewing spots (I also applied a protector to my poor MacBook charging wire, which was another target), and I haven’t seen him even attempting to chew anymore.
I like that these come in different colors as well as different lengths and sizes so you can order as much as you actually need. You just snip off as much as you need for a particular area, so I used a shorter piece for my water fountain cable and a much longer one for my MacBook charging cable to protect the whole area. I ordered the 1/2-inch diameter ones, but you could definitely go down to the 1/4-inch or even 1/8-inch sizes if you’re only planning to cover a single thin cable so it’s not quite as bulky as mine looks above. If you’re planning to cover several cables at once, you’d want to stick with the bigger sizes.”
Get it from Amazon for $8.99+ (available in 15 sizes and 3 colors).