My daughter 9 months old

My daughter first got the hands feet and mouth virus ever since then she’s been with a bad diarrhea, i understand any virus can cause diarrhea but my daughter been really bad literally looks like a waterfall of shit. i had to take her to hospital earlier today because she been like this for 5 days now and today was the worst one you can tell she was in a lot of pain by looking at the way she cry , ( DIARRHEA ONLY HAPPENS WHEN SHE DRINK MILK I GIVE HER ENFAMIL SHE BEEN DRINKING THE SAME FORMULA SINCE 3 weeks old i Breast feed and gave formula till 4 months

So i took her to the hospital and the doctor tells me that her stomach isn’t tolerating the regular milk at the moment to try soy milk and see how that goes

( so my question is has anyone try soy milk with their baby’s and which brand is the best one to buy i like organic things with her just because i don’t trust a lot of brands i feel like organic is better)