Eat this : Apples or fruit, water, coconut water or aloe juice.
Not that :  A burger and beer* at the turn and a sugary sports or energy drink for the back 9.

Dawn says : Hydrate, Hydrate, Hydrate!  A professional golfer once told me you should drink 8 oz of water after each hole.  Yes, that equals 18 cups of water or approximately 9 bottles of water!  Intermixing with all natural coconut or aloe water is extremely beneficial to replace electrolytes lost through perspiration and a much better choice than synthetically sweetened sports drinks.  For a snack, if you happen to roll past a bucket of complimentary apples at the turn, it’s not a bad idea to grab a few to sustain your energy levels as well!

And if your course carries them, energy bars created specifically for golfers on the 1st or 10th tee...
* Beer exception - it's o.k. to consume if you've played horribly on the front.  It might calm your nerves!