Definitely should not be exempt.
There are other options to treat hypos.
I use Glucotabs to treat my hypos. I could not imagine the hassle of carrying around a liquid which, knowing me, I would spill at some point.
But if you want to to use sugary drinks to treat hypos, I think we should accept the tax. As someone with Type 1 Diabetes, I feel I am amazingly lucky to live in a country that provides me with insulin, test strips, meter, etc. The small cost of hypo treatment is nothing compared to the fear that my insurance company would force me to change my treatment just because it is cheaper for them.