What Causes Black Stool And Vomiting While On UTI Medication?

Hi, I've felt ilk the past 7 days. Today my stool was a blackish color. I haven't been able to eat properly the past 4 days everything I eat or drink I throw up. I've been sipping on water, with a splash of peach juice for a little flavor, also ice pops. I had a bad kidney infection last ur, so i took uti medication last night, and feel better. I have been dyhrated so I'm wondering if that's why my stool was a blackish color?