Make sure your nutrition strategy is sound- water on its own is not going to be sufficient for very long runs especially in warmer weather. chewy sweets are good/cheap, but you may want to also add electrolyte tablets to water in order to replace vital salts lost through sweating etc.
Camel back type things are ok but strap rub can be an issue- if you go down this route make sure it is comfortable and fits nicely (ones with the additional link across the chest may be an idea.) You may not like the hot back you get either (this ruled them out for me)
Try taking a bike bottle- it’s what I used to do when marathon training and didn’t bother me. Refillable too, depending on where you run. It also gets lighter so the burdern lessens as the run goes on.
A rough rule of thumb is to consume around 750ml of fluid/hour running. If you are well hydrated when you start you may be able to do a run of 90 mins or so without any in normal conditions, but if longer than this or it is very hot then you ought to start drinking after 40 mins or so. If you get thirsty, it’s already too late.
Same goes on the bike too btw- drink plenty, just like those trendies in the Giro.