Baby drinks

My 9 month old is really struggling with this heat she is super grumpy all the time, she refuses to drink any water atm will just shake it around and spit it, my biggest worry is her becoming dehydrated during this heat, what else can I give her instead of water? Can I put fruit in her bottle of water or just a small bit of no added sugar squash as a one off whilst it’s hot? Even just in a nappy she still seems to be sweating a little bit because my flat is incredibly hot during the summer