Anyone know causes?

I'm 21f and have had a UTI first time recently. To be honest it's complicated but we are trying to figure out what even caused it so would appreciate people letting me know possible causes.

But also I wanted to ask if it's possible that a large liquid intake could cause it if usually I hardly drink anything in a day? I had a lot to drink (all non alcoholic) the day before it hit and literally since my childhood I've never been able to drink a lot so if this was maybe a shock to the system I'd like to know. Thanks all