As previously stated, 'keep hydrated' add something like Staminade powder to you water bottles to replace lost salts and take snacks, I make 'Recovery Bars' and take a couple with me on my bike rides. When your doing heavy work you need sugars to quickly replace the carbohydrates your burning.
GCN recovery bars.
"Sunflower Oil - 120ml/3/4 cup
Soft Dark Brown Sugar - 200g/1 cup
Golden Syrup - 2 tbsp
Peanut Butter - 1 tbsp
Vanilla Extract - 1/2 tsp
Melt these ingredients in a pan over a low heat until melted and mixed together.
Next, add:
Sesame Seeds - 25g / 2 tbsp
Sunflower Seeds - 25g / 2 tbsp
Flaked Almonds - 50g / 1/2 cup
Sultanas - 50g / 1/2 cup
Chopped Cranberries - 50g / 1/2 cup
Gradually stir in thick cut porridge oats/oatmeal - 225g / 8 oz.
Transfer mixture to a baking tin lined with parchment. Roughly 25 x 15cm or 10 x 6 inches.
Press down firmly with a metal fork.
Place in an oven at 180 degrees c, 350 degrees f or gas mark 4 for 10 - 15 minutes, keeping an eye on them so they don't get over done.
Finally, leave to cool in the tin before you take them out and cut them.
Enjoy!"
So these bars have a low GI and digest slowly, stopping the sugar high, remember to keep the fluid levels up too.
You can watch the bars being made,
https://www.youtube.com/watch?v=jMJEIiWV3VQ