+1 on Hillrider's suggestions. I tend to use #3 the most with those types of brakes. I deflate and inflate. Yes, it's inconvient, and there is the cost of pumping it up, especially in the field, but you gotta do what you gotta do. If you try to do Hillrider's #2 suggestion, that might work, but most of the brake levers on a bike of that quality have such a bad cable adjuster or brake lever body that it strips and does NOT stably hold the brake cable with much extension. So usually, I just stick with #3.

You can try #5, but the galvanized brake cable and the poor pinch bolt/nut combination is designed to not survive too much re-adjustments. So if you need to keep loosening and tightening the cable, it's likely to fray/break where the pinch bolt clamps the cable and then the short strands that start to unravel can be a painful reminder of why you should just revert to #3 and deflate the tires when you jab your fingers on the next wheel service.

Remember to bring a cone wrench with 13-14-15-16 mm variable slots and a flat screwdriver. Why? Because if you remove the wheel, chances are you will knock the brake center off and the design of most of these cheap calipers is to be unstable to centering. You need the cone wrench to stick it in the flats where the caliper springs attach to recenter. Count yourself lucky if you have flats. There is an even cheaper caliper brake looking thing that has no flats to re-center. Instead, you take a screwdriver, reach from behind and under the rear stay bridge or under the fork, poke the end into one of the spring coil loops and pivot that side down to push the arch back in place.

And still it may not stay centered. That adjustable crescent wrench is also handy because you can usually use it to bend caliper where the brake shoe mounts so there is a natural toe-in toward the front (helps reduce squeal).