I like sour things. I put lemon in my iced tea. I order my Hot and Sour soup extra sour.
I’ve taken to drinking “shrubs” from the local farmer’s market, and they are pretty sour.
So - how much is too much? How much vinegar or citric acid can be consumed before it messes up your body’s pH?
Gastrointestinal irritation would be the most immediate issue depending on your individual health. A healthy adult can handle quite a lot of acidic foods and drinks without issue.
Dental erosion is a problem. Critical pH for enamel is ~5.5, anything more acidic than that can begin dissolving enamel if it’s in contact long enough.
You would have to consume an uncomfortable quantity of acidic drinks and foods to actually alter your body’s pH, it’s tightly regulated in a very narrow range (about 7.35–7.45) by buffer systems, the lungs, and the kidneys. Food does not directly effect body pH.
So the overall answer is “a lot more than a reasonable person is likely to consume.”
Your body has multiple mechanisms to regulate your pH regardless of what you’re eating. The vinegar , citric acid, etc. are far, far less acidic (that’s the sour you’re tasting) and less concentrated than the stomach fluid your own body produces every single day. That’s all contained in the stomach with its protective mechanisms to keep it from digesting itself. When it travels to your intestine your body modifies it to be harmless to you. Contrary to what some people on social media would have you believe what you eat has zero effect on the pH of your blood and internal bodily fluids.
As noted, the biggest thing to worry about it the effect of acidic fluids on your teeth. Brush after meals and if that’s not possible swish with plain water at the end of your meal.
Following up on the previous good answers: An unbalanced diet i.e. one heavily emphasizing meats, cheese and grains with insufficient fruits and vegetables can slightly lower body pH, but still in the normal range, in the long term potentially having some detrimental effects on metabolism. But enjoying “sour” foods shouldn’t be a problem in those with relatively good health including proper renal function.
Some drugs and poisons can cause metabolic acidosis. Hot and sour soup doesn’t fall into that class.