Avoid excess caffeine. It hastens fluid loss in the urine. While working , take several fluid breaks every hour, drinking at least 1 quart of fluid. Drink as much as you can during the lunch break. Water is your greatest need during work in the heat.
Studies show that workers drink more when lightly flavored beverages are available.
After work , you need to continue drinking to replace fluid losses. Thirst always underestimates fluid needs , so you should drink more than you think you need. Rehydration is enhanced when fluids contain sodium and potassium, or when foods with these electrolytes are consumed along with the fluid. Sodium lost in sweat is easily replaced at meals with liberal use of the salt shaker. Unacclimatized workers lose more salt in the heat so they need to pay particular attention to salt replacement.