What are the alternatives milk for a 20 months old diarrhoea kid?

My Lo is suffering from antibiotics S/E… we have tried Soya milk but it didn’t worked for him. As such, I gave him partially hydrolysed whey protein milk (Similac brand) and mixed it with milo. But I find that Milo’s too “heaty” and “sweet” for him. Dear experienced Mummies, any other alternatives can I use? I’m outta wit! #Alternativemilk #DiarrhoeaKid