You're speaking with Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply.
I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. Please note that such behavior indicates encephalopathy (brain disorder) and encephalopathies can have many different etiologies - inherited such as idiopathic epilepsy, toxicities, nutritional imbalances, and infections (bacterial, viral, fungal), e.g. Trimethoprim/sulfa might be of value (when addressing a bacterial encephalitis) dosed directly into a bird's mouth but would have questionable efficacy when placed in its water. You can google "trimethoprim/sulfa" and find many sites that will sell you powder to dissolve in water but I don't recommend treating birds in that manner if for the only reason that an ill bird won't drink enough to medicate itself properly. The proper form of this antibiotic for birds is a prescription solution of it available through an avian vet such as you can find here: the parrotsocietyuk.org/veterinaryadvice/avian-vets
In the UK, you're likely to run into an additional problem: New rules have prohibited any over the counter antibiotics for birds. Please respond with further questions or concerns if you wish.