Not sugary, but definitely sweet.
HEED is a pure concoction of electrolytes and long chain aminos, but it is sweetened by stevia, which is in fact, quite sweet and has a very unique taste. Note that it is sweet, not sugary. There is a difference. Some people love it, some don't. I don't. I have a super sensitive stomach and dislike sweet drinks while training and racing, so it doesn't work well for me. I have friends who swear by it. I would test it out by buying a small package from a local bike or running shop (since Backcountry doesn't sell single servings) before going for broke and buying a jug. As alternatives for electrolyte replenishment, you may want to also try nuun or Elete.