I like a product called Nuun. It is an electrolyte tablet you dissolve in water. It has no sugar and tastes good!

Depending on the intensity of your training, you may find that you need carbs during exercise. Anytime I have a long session - 1.5 hours or more of moderate to high intensity - I find I need about 50 - 100 calories per hour of pure carbs (like a gel) to get through comfortably. This is far less than many athletes who don't do low carb ingest, but I find it works for me.

Good luck with your triathlon! I did 4 triathlons last year. They're addictive!