Sudden acid reflux can be caused by a variety of factors, including certain foods and beverages, obesity, smoking, stress, pregnancy, certain medications, and certain medical conditions. Certain foods and beverages, such as fried foods, citrus fruits, tomatoes, caffeine, chocolate, and alcohol, can trigger acid reflux. Obesity can put extra pressure on the stomach, causing stomach acid to flow back up into the esophagus. Smoking can also increase the risk of acid reflux. Stress can lead to an increase in stomach acid production and can also cause relaxation of the lower esophageal sphincter, allowing acid to reflux. Pregnancy can cause relaxation of the lower esophageal sphincter, and certain medications, such as ibuprofen, aspirin, and some blood pressure medications, can also trigger acid reflux. Certain medical conditions, such as asthma, diabetes, and GERD, can also bring on sudden acid reflux.