BEFORE I work ( or fish) in the heat I drink some orange juice - that loads me up with potassium. That helps a lot. But you still need to carry a source of water and electrolytes with you. Even if you carry Gatorade, also carry some some orange juice or other fruit drink. Look at the label of the drink - it will tell you the potassium and sodium content - and choose something that has some sodium and lots of potassium.

Pete