Give them some pediatric electrolyte fluid to keep them hydrated. Try giving them popsicles or italian ice. It will help hydrate them and the cold may help with their throat.
If you want to try to get some soft foods into them, I suggest a really cold drink (like an icee) or having a popsicle first. This will help numb the throat a little.
You could also try serving them their formula cold. Make it ahead of time and refrigerate it. It might feel better going down.
Don't be surprised if they only take a couple of tablespoons of fluid at a time. Also, keep track of their diapers. If they don't have any wet diapers in an 8 hour period, call your doctors immediately. When my kids had sore throats with vomiting and diarrhea (my 3 year old when he was younger and my 7 month old 2 months ago), my doctors told me not to worry about the formula or regular food for the time being. They told me to concentrate on the fluids. Keep pushing clear fluids.
Anyhow, if you have any questions or concerns, please feel free to call your doctors office. That is what they are there for. Most doctors (especially pediatricians and their staff) are very understanding and would much rather have you call with a concern than wait and have it get worse.
Good luck with your little girls. Try to get some sleep when you can and eat right so that you don't get it too. I hope all of my experiences help you out.
PS. Had to come back and add this. If you take the one Mom's advice and give them Gatorade. Remember to water it down, half Gatorade and half water. I was told this by my sister who is both a nurse and has a bachelor's in physical education. The Gatorade is too strong for their little bodies to process correctly if you don't water it down.