First of all, you can consider selling the treadmill on the second-hand trading platform. In this digital age, many people are looking for second-hand fitness equipment, and second-hand treadmills with lower prices are usually very popular. So when selling idle treadmills, you need to give a reasonable price, and give enough descriptions and photos in the advertisement.
Secondly, you can donate the treadmill to charity or public fitness places. If your treadmill still works, give it to those who need it, especially those who can't afford fitness equipment themselves. You can contact local charities to find out if they need this kind of fitness equipment. It can also be donated to public fitness places, such as parks, schools and gyms.
Finally, you can consider changing the treadmill into an interesting DIY project. You can turn it into an ornament to decorate your home, or use it to make a home fitness equipment. You can find some videos and tutorials about treadmill DIY, learn and try to create your own works.
In a word, an idle treadmill is not necessarily just useless garbage. You can sell it to people in need, donate it to charity or public fitness places, or transform it into an interesting decoration or DIY project. In this way, you can not only easily solve the problem of idle treadmills, but also help more people.