One person wrote that he used oranges. If you could find some citric acid to add the added acidity might help. Hve you looked at Dr. Sutter's coke flush?
There is a Ask Dr. Sutter Forum so you can ask about alternatives to lemon.
Dr Sutter’s Olive oil, coke, lemon, Liver Flush | The Cure Manual
Dr. Sutter is one of the experts at Curezone.com and he shared his Liver Flush protocol using of all things... Coca Cola! If it works, it works. This is