Recurring UTI's??? softdrink?

I'm 18 and had a UTI a few weeks ago. I took the antibiotics and it seemed to go but a few days after I took the last pill I stayed at my bf's and didn't drink anything and didn't go to the toilet and had a coke before I went to bed and I woke up in horrible pain with another UTI...I seem to get them when it's cold, when I'm at someone elses house and I drink soft drink? Can these cause UTI;s or do I just have a weird body and why did I get another one so close to the last one??? Please help!