drinking while running

My usual running day is 4-5 hours. I am slow. So what I will be using on my runs is cycling jersey with food in the pockets and water bottles. I will finish running in april. Then cycling. The hydration on my cycling is as usual. 2 water bottles on my bike and some food in my pockets. cycling will take 2 months. So when i start the running part of the duathlon it will be hot in Maimi in jun. So I am planning to run then with a hydro pack. I have used hydro pack doing cycling. First time using it running.