Could One Drink Water Before An Endoscopy While Having Lingering Symptoms After H. Pylori Treatment And Fluctuating BP?

Hello all specialists, My mother 54 years old has diagnosed with H. Pylori and on the treatment with Talicia for 15 days! She has finished the treatment on Nov 17, 2021, but she still get the dry/thirst in mouth, her throat when sip a water or finish some foods always get the sound of boiling water in ber throat. My mother also always get dizziness, double vision if stand for too long or doing something heavy! Not to mention, her blood pressure since on the treatment to finished the treatment always inconsistency around 80/66-100/68. My mom will get endoscopy on Nov 30, 2021 at 1 P.M afternoon. Any advise for my mother to get back to normal blood pressure because I worried she will get faint easily if she get fasting for her endoscopy. Can she drink some clear water during fasting or eat some light foods? I really appreciate your input specialists/doctors!