The worst thing you can give a bird with sour crop is antibiotics. You want to read up on sour crop before you start telling people what they are saying is rubbish.
Sour Crop is also called Candida, or Thrush. It is a very common disease, caused by a fungal infection of the digestive tract. It’s often associated with excessive use of antibiotics.
Symptoms of Sour Crop include listlessness, loss of appetite, weight loss, a water-filled crop, and frequent vomiting. The vomit often has a very putrid odor. Sometimes in lesser cases, thrush will show itself as just small whitish spots in the throat, which can cause confusion with Canker. Another symptom, not often noticed, is feather pulling in adult birds.
To prevent Sour Crop, avoid overcrowding, maintain a sanitary loft, and do not medicate indiscriminately, especially with antibiotics.
http://www.siegelpigeons.com/asked-sourcrop.html