A freshly opened canned beverage will provide the most carbonation. To burp loudly you will want to drink the beverage as fast as possible. Choose something that you like, so you’ll want to drink fast. Be careful that it’s not too sweet, or it may upset your stomach.  Pick a drink that is cold but not so cold that it hurts to drink quickly. Avoid drinks that have gone flat and have been open for a long time. The more carbonation you are able to take in, the larger the burp you can release will be. Take large back to back gulps of the drink, and try to finish it in one attempt.  You don’t need to take large mouthfuls, smaller sips will introduce more air as you swallow. Resist the urge to let out small burps as you drink. Make sure that all of the beverage is at the bottom of your stomach and the gas bubbles have had a chance to rise. Make a straight pathway from your stomach to your mouth by extending your shoulders upward and stretching your back. You want to allow the gas travel as smoothly as possible from your stomach out in order to produce the loudest burp. Let the accumulated gas go all at once. The sound of your burp will reflect the amount of air you are releasing from your stomach.  Open your mouth. Squeeze your stomach muscles similar to the feeling of vomiting. Let the air escape your stomach. Amplify your burp by pushing more air out faster. Use your abdominal and stomach muscles to squeeze your stomach to push out a larger volume of air.

Summary:
Choose a carbonated beverage. Drink the beverage as fast as you can. Wait for 3 seconds to let the drink settle. Stand up or sit up straight. Release the burp. Squeeze your abdominal muscles as you burp.