It could also be that the high intake of the soda is affecting his kidney function, which would initially show up with the symptom of elevated blood pressure. Yeah, the sugar is not good, either, but if the doctors did not see a specific problem with elevated blood sugar, they may not be focusing in on that part of it as the issue. Part of the problem is that doctors don't typically treat until there is a problem, then they prescribe a pill for it. A lot can be done to prevent chronic illnesses, but there is not much focus on preventing illness (unless you really get a good practitioner).
Anyway, just my "off the cuff" observation here, as there is probably a lot more to the story than what you have written.
Metabolic syndrome is really a group of several risk factors that converge together that increases the risk of stroke, heart disease, and diabetes.
Metabolic syndrome is present if you have three or more of the following signs:
-Blood pressure equal to or higher than 130/85 mmHg
-Fasting blood sugar (glucose) equal to or higher than 100 mg/dL
-Large waist circumference (length around the waist):
-Men - 40 inches or more
-Women - 35 inches or more
-Low HDL cholesterol:
-Men - under 40 mg/dL
-Women - under 50 mg/dL
-Triglycerides equal to or higher than 150 mg/dL