I’ve always liked the idea behind the camelback style backpacks as they take away the whole thing of dealing with drinks bottles while enjoying yourself outdoors. The backpacks have been around for what seems like an age and have been reproduced by other makers over time.
The only issue for me is the packs themselves are a little on the small side for the amount of camping equipment I carry (even more so in the winter).
If your only interested in the water storage side of things without having to plump for a full rucksack, I’ve just found these stripped down versions on eBay that give a large 2 liter storage.
The bladder looks slim enough not to get in the way while you out exploring.
I’m excessively paranoid about water bottles thrown into my pack as there’s normally a mix of gear in my bag including Go Pro, digital camera and a bit of radio tech for those lovely high mountain camps and any leakage is going to make for a very expensive day!
Just what can you put in the bladder?
I imagine that’s a question of how long you want the bladder to last/be constantly reusable..
Anything corrosive is going to cause problems down the line and although you may be happy filling the bladder up with a good beer for those summer hikes (very nice, but may be a bit warm after a while though).
Sticking with straight water is always a safe choice as any flavored liquid will mean doing a great deal of maintenance to make sure the bladder is clean for the next trip out (please someone invent a self cleaning one).