At the end of a walk we all go back to the van and have a drink - on really hot days we carry water as well, stopping to sip little and often. The dogs get the aquabowls, which are fantastic! I love my road refresher bestest of all for travelling in the van, but for getting water to the dogs quickly at the end of the walk, these are great. They don't need taking apart to refill, and as I got the big ones I just bring one indoors to refill every couple of days. To operate, just open the valve, stand on one end, and let the dogs at 'em.
Big or small dogs can use them with no problems - sometimes I put them on the floor of the van for the bigger dogs. They don't all appreciate it, but some do. I don't take them on a walk as they are not very comfortable to hold and it means one hand is 'wasted', I use a smaller more portable carrier.
Bit worried about Scarlet licking her lips while looking at Max...
I use my water bladder in a small backpack, attached to the back is my powermonkey explorer, which charges while in the sun and I can use it to charge my mobile phone while I'm out. I can't find the photo now, but I'm sure it can be imagined.