declogger liquid clears up blockage inside the pipe, but that's also assuming the clog is not severe.
The bottle trap catches debris to ensure it does not go down the drain pipe. When your sink clogged, the first and easiest troubleshooting you do is to open up the bottle trap and pour away the content, then clean out any object that is stuck inside.
All you need is a bucket and glove. Just turn the slip nut and remove the bottle.