It looks like a Dracaena Janet Craig....from what I know this plant enjoys bright light with part shade but not direct sun if outdoors..moist soil but not too wet feet, some humidity. Sometimes it starts going brown maybe due to overwatering/underwatering and being cold. Suggest keep her warm and indoors but near a window where she can get bright light. You mentioned you have put it in a jar of water? I would remove it from that set-up and stick it in a container with soil instead. Dracaena's hate being cold.
