your best way to be hydrated is plan ahead. drink plenty of water the night before, or at least a few hours before, to let your body absorb and store it properly. when you pee, if it's clear like water you're good. keep drinking water frequently, but not too much at a time. for work in hot conditions, about 16 ounces water every 1/2 hour and a Gatorade or Powerade every 2 hours works good for me.