If you're involved in a field of science or work in a laboratory, a beaker means you're focused and passionate about your work, study or scientific endeavors. Your mind is simply mirroring and reflecting even in your dreams, either out of habit or because you truly enjoy what you do.
If you have no relation to aforementioned careers, try to remember what the beaker contained. Is it something good or bad? If it contained (you were concocting) something good, it may be a symbol of something positive and productive brewing in your life. If it is of something bad, you may be searching for a way to unload unwanted things or leave someone in your life.