I looked online a little and it seems there is something called sulphur burps. Basically foul smelling burps that are due to eating sulphuric foods,,,,,,and sweet potatoes were listed.
Here's what I found...I don't think it's harmful, just doesn't smell so great. Unless there is a serious underlying medical problem, like Celiac's disease or Crohn's, and obviously a dr would need to diagnose. I haven't had a chance to look into much more, but thought this was a good start.
Sulfur Containing Foods
Removing sulfur containing foods from the diet may reduce the smell of sulfur burps:
Sulfur containing food preservatives, like guacamola, often used on dried fruits, salads in hotels, meat in fast-food restaurants or in pre-prepared canned foods
Dairy products, especially milk
Vegetables: asparagus, broccoli, cabbage, garlic, mustard, onions, pack choi, parsley, sweet potatoes, Swiss chard, tomatoes, watercress, yams
Legumes: beans, peas, lentils, soy, carob, jicama, alfalfa
Fruits: avocado, bananas, watermelon
Grains, nuts and seeds: corn, sunflower seeds, oats, cashews, walnuts, almonds, sesame seeds, coconut.
Tea and coffee
Amino acids: cysteine, methionine
Vitamins B1 (thiamine) and H (biotin)
Certain medicines may contain sulfur (also check labels for amino acids cysteine or methionine that contain sulfur).
Sulfur Reducing Microbes
Examples of sulfur reducing bacteria and some other microbes that can use sulfur compounds from the food and yield hydrogen sulfide as an end product:
Helicobacter pylori, a bacterium causing chronic gastritis, gastric or duodenal ulcer, upper abdominal bloating, heartburn and burping. H. pylori is diagnosed by urea breath test; treatment is by antibiotics.
Giardia lamblia, a one-cell parasite, usually contracted by food or water poisoning, causing diarrhea, bloating, foul smelling burps or farts. For diagnosis and treatment read about human intestinal parasites.
Intestinal bacteria that are part of normal intestinal flora but can cause bloating, burping, flatulence or diarrhea when they overgrow; condition is called small intestinal bacterial overgrowth (SIBO) . SIBO may be also present in lactose intolerance or fructose malabsorption. In certain diseases like celiac disease or Crohn’s disease, foods may not be digested completely and can be therefore broken down by sulfur reducing bacteria that produce hydrogen sulfide.
How To Get Rid Of Sulfur Burps?
Remove as much as possible sulfur containing foods from your diet. This may reduce sulfur smell of burps and gas in a day or two. After that, you will still need to find the cause of belching or gas themselves.
If you suspect you might have celiac disease, besides the low-sulfur diet, try a gluten-free diet (no wheat, barley and rye). If your symptoms disappear or lessen considerably within a week or two, this speaks for celiac disease.
If you have history of peptic ulcer, stomach burning, gastric reflux and heartburn, visit a gastroenterologist and ask for a breath test for Helycobacter pylori. This bacterium is a common cause of sulfur burps. Treatment is with 7 or 10 day course of antibiotics.
If you are bloated and have excessive foul smelling gas or loose stools with mucus, ask your doctor for a stool test for ova and parasites (O&P) since you may have infection with a parasite giardia. Treatment is with anti-parasitic drugs.
If you suspect Crohn’s disease - symptoms include low grade temperature, nausea, fatigue, blood in the stool, diarrhea, bloating - visit gastroenterologist and ask for appropriate tests that may include colonoscopy.
If all above tests are negative, ask for breath test for small intestinal bacterial overgrowth (SIBO) .
Gastric emptying test may reveal slow stomach emptying (gastroparesis).
Some people with gallstones reported that sulfur burps disappeared after gallbladder removal. Diagnosis of gallstones is with abdominal ultrasound or other gallbladder tests.
To get rid of sulfur burps, sometimes you only need to remove some particular food(s) rich in sulfur, for example, Pina Colada, containing coconut cream.
If you have sulfur burps but NOT sulfur gas (flatulence) the cause is probably in your stomach (H. pylori infection, gastroparesis). If you suffer from both sulfur burps and gas or only sulfur gas you may have small intestinal or gallbladder disorder.
Pepto Bismol (bismuth subsalicylate), a popular antidiarrheal drug, binds hydrogen sulfide and removes it from the gastrointestinal tract thus reducing sulfur burps and gas. Pepto Bismol should NOT be used in children, and no longer then 2-3 weeks in adults. Pepto Bismol usually colors your tongue and stool black.