While drinking water is one of the healthiest things you can do, drinking water frequently is not an effective way to help prevent COVID-19.
The suggestion is that drinking every 15 minutes would wash any virus down the esophagus so it can’t get into our lungs. When we’re exposed, there are at least thousands of viruses that we come into contact at any given time. It’s highly unlikely you would wash all that virus down your throat and ultimately into your stomach.
The primary way the virus is transmitted is through respiratory droplets in the air, directly into the respiratory system. Chances are that some of that virus would have already made its way into your nose before you start drinking water. Plus, we often contaminate ourselves by touching our nose, allowing the virus to immediately enter our respiratory tract.