the heat can do a number on your appetite and cause u to not eat. ull need calories, electrolytes, and other nutrition to feel good throughout the day. so make sure to eat.
drinking something other than straight water can help. Gu, Scratch, Nuun, etc. itll all work some, esp if u have a problem eating. im currently a fan of Gu Roctane cuz of the added BCAAs. plus, this can help u from overhydrating if you obsessively keep drinking.
i keep a wet towel in the drink cooler with ice for my neck and i make sure to keep my undersuit wet.