“How can I lower my blood pressure instantly?”

I am assuming you are asking about non pharmacologic means of lowering blood pressure since there are many medications given sublingual and intravenously that can almost instantaneously reduce BP (SL NTG, IV Hydralazine, IV Nitroprusside, SL Nifedipine etc). Biofeedback and progressive relaxation exercises can rapidly bring down BP non pharmacologically. By mouth meds such as Clonidine can lower BP in 30 minutes.