Broken Hip, Unable To Walk, UTI, Bacterial Infection. Medications To Treat This?

Hi, My Mum is 95 years old, she is confined to bed for most of the day as she cannot walk after breaking her hip 20 months ago and has to be hoisted. Our problem is when we think she may have a UTI , which she has been prone to in the past, there is no way to get a urine sample to check if it is a UTI and if so, which bacteria it is. Is there anything we can do other than try different antibiotics in the hope they will work? We know she should be drinking more than she is at present in order to avoid UTIs, would you have any suggestions how we can remedy this? Thank you.