Why Did I Experience Unconsciousness and Rapid Heartbeat After Drinking Water as a Type 1 Diabetic?

Hello doctor Name:- Anshika Age:- 18 yrs 3 months Sex:- Female Medical Problem:- .I am a type 1 Diabetic, Morning I took 10u of Novarapid and had breakfast. After giving my practical exams which was of 2 Hours, In Afternoon I was walking to the station, I was extremely thirsty so I got buttermilk, after reaching the station and when the train boarded, I was still feeling thirsty, I checked my Sugars it were 250 so I took 15U of Novarapid because I wanted to eat food as well. After reaching to my destination that was just 15 mins, I bought Cold water, after having it, i felt a little discomfort in chest. I was walking on the bridge to the metro and suddenly I started feeling Unconscious, My sugars were not low because I took insulin 5-6 mins ago. I had a rapid heart beat, My hands were shaking, I was scared, I was dizzy and wanted to sit down, I had a feeling of passing out. ECG was done. Blood pressure was high that was 150/80 mm hg but later it got normal. The doctor was about to give me some injection to lower blood pressure but later didn't. I was not satisfied with doctor.