This is the reverse of the DIY aircon, but it works just as well. Air conditioning can be a nightmare in hotels. It can leave your skin dry and your throat sore. While opening the windows can help, the main problem is the air con itself. So, grab a towel, and let's fix that. You'll need to run your towel over a warm tap and squeeze it until most of the water wrings out.
Now, lay the towel near the aircon while it's on. The air will filter through the moisture and act as a humidifier. However, we advise you not to do this when you're asleep. For safety reasons, it's never wise to leave towels over electronics unsupervised!