Most people have too little stomach acid not excess. Apple cider vinegar and betaine HCI (hydrochloric) supplements are treatments for insufficient stomach acid.
Excerpt from Gallbladder Attack article on low stomach acid...
"If you're nervous about trying supplemental hydrochloric acid, you can do a trial with 1-2 TBSP of organic apple cider vinegar mixed with 1/8 to 1/4 cup of water after a meal. If it makes you feel better and does not hurt, you most likely would benefit from taking 500 - 1000 mg. of Betaine HCl with your meals.
Diseases Associated with Low HCl (low stomach acid):
Asthma
Diabetes
Osteoporosis
Arthritis
Hepatitis
Eczema
Acne rosacea
Dry Skin
Psoriasis
Parasites
Gallbladder disease
Herpes
Hives
Hypothyroid
Hyperthyroid
Thyrotoxicosis
Autoimmune disorders
Lupus erythematosus
Myasthenia gravis
Pernicious anemia
Celiac disease
Sjogren's Syndrome"
Apple cider vinegar is a way to cleanse the body and balance acid and alkaline, but it doesn't increase stomach acid on a permanent basis. Betaine HCL is used for gallstones, not for stomach acidity, since it doesn't do that either. The reason is that neither stays in the stomach, so it can't permanently alter the acid/alkaline balance. The caution about HCL is more about using pure HCL food grade. It's hard to use and must be refrigerated; it's hard to find except in the best small health food stores, and has caution labels all over it. Betaine HCL delivers a lot less HCL, and there's no proof it does anything about the regular ongoing amount of stomach acid. When these things help, we often don't know exactly why, but it's more a treatment of symptoms than a permanent alteration of stomach acid. Apple cider vinegar does, however, help in it's other uses, such as cleansing and balancing. The only known way to permanently alter the acid level in the stomach is to eat differently -- for example, the stomach produces more acid if you eat more protein, since it needs more acid to digest protein. To digest other foods, it needs to be akaline -- it would be, therefore, unhealthy to always have a high level of stomach acid. So if the apple cider vinegar is helping, stick with it. There are other treatments for reflux as well. A holistic nutritionist can help reorient the diet to your new circumstances to better maintain something close to a normal acid/alkaline balance in the stomach, but obviously it will be harder without the gallbladder in terms of digesting fats particularly. Good luck.
Oops. Brainfart. Confused HCL with food grade hydrogen peroxide. Disregard that part of the above comment. Also, one way to increase stomach acid in the wrong way is the regular use of Tums or other acid suppressants -- they just force the stomach to make even more acid in a rebound effect, but not when you want it to. Again, stick with the apple cider vinegar.