A soft-drink can filled with a few bolts, coins and pebbles, when shaken, will make a racket to vex a coyote away from you and your dog if this should become necessary. The standard soda-can shaker is rather bulky to carry on your walks. I have found that using a much smaller 5.5 oz. juice can makes just as much noise as the soda can and can easily fit into a pocket. I tried to find an even smaller alternative and came up with a loud clicker. Although this can have a sharp and penetrating sound, even a very loud one will not be as effective as the shake-can.
In all my years of watching coyotes, I have never ever had to ward one off. A coyote might approach in your direction out of curiosity, but it will keep a safe distance because coyotes do not want to tangle with humans. However, if you have a dog, you may feel more secure in a coyote area if you have the can on hand, especially during pupping season. Coyotes have come in close to some of the dogs in our urban parks for various reasons, as I have discussed earlier. The shake-cans have loud and sharp sounds, which, along with your vigorous activity of shaking the can, might serve as a “double” vexing agent. Of course, ultimately, flailing your arms and any sharp sound, even screaming or yelling, will serve the same purpose to increase the distance between you and a coyote who you feel has come in too close to you.