Based on my research, there doesn't seem to be much to the Acid/Alkaline theory. However, based on my experience, there seems to be something to the theory.
My experience: I've been able to alleviate my gout attacks last three times by drinking baking soda dissolved in water. This is courtesy of anecdotal accounts of getting out of gout attacks by rapidly changing the pH.
The latest thinking is that gout attacks are not actually triggered by high fructose consumption or high serum uric acid levels but the acid-base imbalance. That is, while fructose consumption may increase uric acid levels, to actually precipitate a gout attack, you need to deviate from the narrow band of normal blood pH range: 7.35 to 7.45. Ideally you wanna be at 7.45 or slightly above. If you're close to 7.35, you would be in "acidemia" and vulnerable to gout attacks, if you're genetically susceptible to gout (I'm, according to 23andme) and/or if your uric acid is high.
Another way of measuring the acid level is to test your urine with pH test strips (I've ordered some from Amazon): keeping your pee's pH equal to or above 6.8 could stave off gout attacks, especially at night while sleeping (which is when gout attacks typically occur) when the stomach is not producing any juice -- "acid tides". This is what the above site claims (and I do concur with its findings based on my experience).
During recent gout attacks, instead of taking NSAIDs (prescription Naproxen), I drank 3-4 tbsps of baking soda dissolved in water over 4-6 hours. Each time, the attack went away in about 3-4 hours. Had I taken NSAIDs, it may have taken somewhat longer. (Given my autoimmunity and apparent dysbiosis, I'm trying to stay away from NSAIDs by any means). The baking soda seems to have done the trick by turning my body alkaline quickly. Now I'm trying to permanently cure myself of gout by conducting an extended experiment with the baking soda, complete with monitorying my pH levels (urine and saliva) daily.
So what kind of bearing does this have on the acid-alkaline theory? I remember several past gout attacks which followed my having been out in the cold without proper clothing or when I exercised too hard -- in other words, when my pH balance would have been disturbed through external factors. Altering the pH through internal means (i.e., diet) could be another way of triggering gout attacks -- by eating too many acid-forming foods: several of my attacks followed after eating bacon (there is no question bacon was responsible for some of my attacks). But the point is that the bacon may have raised my uric acid AND pushed my body into acidity. It's a two-prong phenomenon.
Look, most conventional medicine folks believe purines are behind gout. They tell you to cut back on red meat and especially organ meats, which are by definition acid-forming and raise the uric acid. Aren't we really saying the same thing here? Taubes and Johnson might be right that it is really fructose that's really behind the elevation of uric acid (rather than redmeat). But even with uric acid elevation, you need the pH tilting toward acidity -- this could happen by being out all night or eating beef liver or kidneys. Before pooh-poohing the acid-alkaline theory, it might be that there're kernels of truth in all theories that are more or less overlapping. You'll see that if you examine these closely: low carb vs. high carb; processed carbs vs. whole food carbs; low-glycemic vs. high-glycemic; n-3 vs. n-6; low PUFA vs. high PUFA; low sugar/fructose vs. safe starches; low salt vs. potassium/sodium balance.