Brawndo has electrolytes.

When it is very hot your body loses said electrolytes through sweating. So yes, they do.

When I worked on construction sites in the summer, nothing tasted better than a Gatorade at the end of the day.

Although that was the 80s when they only had green (lime?) or orange flavours, and they seemed more like a real taste. Now the product flavours don't seem like anything.

Our bodies often know what they need. Cravings are often how they communicate it. Electrolytes taste amazing when you need them.

Interestingly, our brains seem to contain a fairly good lookup between smell and nutrition. An interesting diet I've seen is to get a good selection of fruit and vegetables. For each meal, sniff them. If any smell particularly good to you, base a meal off of them.

It seems like it to me, whenever I work outside in the summer

It's called pika