Salt gets the most blame for causing high blood pressure, but it actually is not what comes out of the salt shaker that's the problem. In fact, it is one of many factors that create the situation, and a lot of it is dietary.
Sodium : Salt is a combination of two chemicals, sodium and chloride. This can make things confusing, especially when looking at prepared foods. The label does not say salt; it says sodium.
There is even more confusion when you start looking at studies. The theory that sodium increases blood pressure has to do with it causing more water in the blood stream. There are some studies that suggest that's true. There are also studies that suggest it is not. This is a discussion best held with your doctor.
Dehydration : It may seem odd that dehydration would have any effect on hypertension, but it does. Small capillaries are closed off and this raises the pressure on the major blood vessels. This increases the numbers and can become deadly.
Caffeine : While we do not know why caffeine spikes pressure levels we do know that it does. This is true even for the healthy. Repeated exposure to caffeine can make it a real problem over time.
Things that Help : What we eat or drink can have a positive effect. Garlic is a good example. While it's best taken raw, garlic supplements are more palatable. You will still have the odor problems garlic produces, but at least it will not burn your mouth and stomach.
Maintaining hydration is very important. Water is great most of the time, but if it is extremely hot and / or you are exercising vigorously you may need a sport's drink. These maintain electrolytes, another problem that dehydration can cause.
Talk to the Doctor : If you have hypertensive or suspect you do, talk to your doctor about the things you can do to keep your numbers in the right range. There may be other suggestions, and you may need medication to help.