There is no evidence that a special diet will accomplish anything but diminish your dad's pleasures. I would recommend you permit him to eat anything whatsoever his heart desires. Including Coca-Cola and Mountain Dew, if he enjoys these beverages.
All blood pressure medications have side effects. I believe your dad's physicians have taken this into consideration, along with his personal wishes.
One thing to remember is that "blood pressure" medications, in general are appropriate onloy when the blood pressure is consistently high. A medication that is appropriate when the blood poressure is 190/100 may increase the chances of death when the blood pressure drops.
With blood pressure the decision is whether or not the pressure changes are compensatory (reacting to body needs) or idiopathic (of unknown etiology). Sometimes it's six of one and a half dozen of the other. Blood pressure readings without knowing the pulse rate and rhythym are meaningless.
Good hydration is in general, good medicine, if the problem is dehydration.
Bear in mind that as some malignancies metastize, they may cause irreparable damage to the body's regulatory system. And this damage may involve inexplicable irregularities in blood pressure.
I would not be so quick to condemn his physician or to agree that he has been receiving inferior care. It doesn't hurt to get a second opinion. but many patients make conscious decisions not to take unpleasant medications, and these decisions should be respected.
Your interest in his care is commendable, and I do not mean to diminish your concerns. This is a complex and by no means uncommon experience.
Maintaining control over one's life is very important, and I would give careful consideration to your dad's wishes and not assume they are irrational.
hi, I know one doctor that can/may help you, he's location is in Cubao. if you're near there you can see him during Saturdays, or weekdays afternoon, depends upon his schedule. I can only give you his address, maybe the land phone too, but let me know if you're interested. too much medicines can complicate your dad's sickness, make him drink lots of water (specially alkaline water), one glass (normal glass) every morning before taking any food or any thing, then after every hour, then 1 glass before he sleeps, then put 3 grains of rock salt in his tongue (at the top), let the salt melt in there. It will help him normalize his BP somehow... Only water is to be drink, nothing else. if he can, eat only vegetables and fruits, fresh only, not cook, not steamed, he can eat as much as he wants but only fruits and veggies.