My job is a mixture of working on site and in the office. At the moment it is hot, and working onsite in 40+degree heat for 5 + hours a day is taking it out of me.

I and easily drainking 3-4litres of water, but I feel my energy levels are low and by the evening I am buggered.

At what point should I be drinking something other than water, perhaps a cordial or something that had a bit of suger or electrolytes? I try to avoid that sort of stuff as it isn't very healthy but I also don't want to be feeling so crappy

Hopefully someone can help me out
TIA xxoo