Lay off the coffee and tea. They dehydrate you. Days I go out to work I just have one cup of tea.
As pointed out hydrate before you hit your first job. Clear piss indicates you are hydrated. Any trace of yellow and your body is not fully hydrated.
So put that water bottle in your cup holder and keep drinking soon as you start your day.
Besides bringing enough water to drink. To help stay cool after I finish loading up and just before I drive to my next job, I take out a gallon of water just to pour some water over my head and wash the sweat off my face, and rinse off my forearms.