If you use the search function within this sub for “zero calorie drinks” or “diet drinks” you’ll see tons of answers to similar questions! In general some people think it’s fine, as long as no-cal you aren’t breaking fast; other people think anything with flavor will create an insulin response.
Personally I think with an 8 mile hike and elevation you should make sure you’re getting adequate electrolytes and hydration, so assuming your drink has electrolytes I’d go for it! And lots of water.