Sugars (soda) and fermented yeast (Beer) feed bad bacteria and yeast like e. coli and candida. Bi-products of their feeding is gas which is what relates to the IBS symptoms like flatulence, burping, abdominal pain, bubbling, and when more extreme/chronic diarrhea and constipation. And when more extreme...well my personal theory is abdominal abscessing. Watch you don't overdo the carbs, FODMAPs specifically.