Does that mean that you need to carry water with you wherever you go? Not necessarily. Take water with you if you are spending extended periods of time in a hot or dry environment. Also, bring water if you are going to be active (this includes everything from hiking to shopping). When you are working out, especially for prolonged periods of time (such as hiking or biking), then take in small amounts of water regularly to keep your water output (sweating, etc) equal intake, and your hydration level steady.
I like to spend time outside in the summer, so I have many different bottles and hydration systems.
My favorite water bottle to take to the office or to the park is the Klean Kanteen. I prefer the stainless steel to aluminum because aluminum leeches into the water and is toxic at high enough levels. Though aluminum bottles (such as Sigg) are coated on the inside, the coating can be scratched or worn down.
I also like Nalgene containers. If I am dehydrated and want to keep a better eye on my water intake, then the gradient on the side of the Nalgene water bottle is very helpful. Further, the big Nalgene water bottle holds a full 1L. I like the wide mouth bottles because they fit onto most water purifiers, so I can take them camping. It's also easier to add ice into a wide mouth bottle, and they're much easier to clean. The wide mouth bottles are a little harder to drink from. I usually just leave a bendy straw in the bottle and use it when I'm drinking.
I also really like the Camelbak water bottle, which to me is like an adult sippy cup - it's impossibe to spill water all over yourself and your desk. So if you're a clutz like me, then this is definitely a winner. The only problem with this bottle is that the cap is difficult to clean thoroughly, so I use mine only for water. It is also important to note that when buying plastic water bottles, you should look for ones that are BPA (Bisphenol A) free.
No matter what water bottle you choose, make sure you keep it clean. I use my bottles for water only, and hand wash them, since the dishwasher tends to degrade them. I have special bottles for sugary liquids, such as my morning shakes and gatorade - these get extra cleaning. Also, don't drink any water that has been sitting for too long, as bacteria does grow in water. As for water sources, I think tap water is fine. Plus it contains the flouride we need to keep our teeth healthy. Recent studies have shown an increase in tooth decay due to the lack of flouride in bottled water. If you don't like the taste of your tap water, just boil the water (will get rid of the chlorine), and then store in the fridge.
And yes, all of my water bottles are pink - hence the girly tomboy title!
I also really like my hydration packs. I use these for hiking and biking. It's easy to sip water regularly when there is a tube three inches from your mouth that you can drink from. My favorite hydration pack is the Dakine Nomad, which has special straps for my bike helmet (great for commuting) and knee/shin pads (which I carry for when the trail unexpectedly turns nasty). I like hydration packs that have some storage, for a long sleeve shirt, a bike repair kit, and trail mix or even lunch. I appreciate the Nomad's front pocket with an organization panel useful for a pocket knife, flashlight, and other bits and bobs I take with me into the woods. This pack even has a padded pocket for my camera. The pack holds a 3L resevoir.
I also have a Camelbak MULE, which I also really like. I think Camelbak makes the best water resevoirs. The MULE also holds 3L of water, and has enough compartments and straps to fit all of the extras that I bring with me. I like that the Camelbak has a waist strap, which is nice for hiking.
Both Camelbak and Dakine make women specific hydration packs which are shorter (for shorter torsos) and are designed for narrower shoulders. As a tall (5'10'') ex-competitive swimmer with broad shoulders, the male specific packs fit me better. But if you have narrower shoulders, then definitely look at the women specific packs. Go by fit first and foremost. If your hydration pack fits properly, you won't even notice you're wearing it - until you take it off after a long bike ride and there is a huge sweat stain on your shirt in the shape of your pack. Yes, that's experience talking.
Avoid putting sugary liquids (such as gatorade) into the hydration pack resevoir, as it is somewhat challenging to clean. Always rinse the resevoir after use, and hang up open so that it dries. In the summer when I'm using my hydration system regularly, I just keep the resevoir in the freezer to avoid anything growing in it. Camelbak makes cleaning brushes that clean both the resevoir and the tube, which is very useful. Although once you get stuff growing in your resevoir, which I have, it's very difficult to get rid of permanently.
For extra long days or extreme heat, consider electrolyte replacement. I really like the Camelbak Elixir tablets, which have a bit of flavor but do not have any sugar. I have used these in my hydration packs and they're fine - no problems with any kind of growth or yuckiness. And I do like the taste. When I lived in Arizona and mountain biked in the desert, these made a huge difference! They're not cheap, but they're definitely worth it.
And if you're enjoying the great outdoors with your doggies, don't forget to keep them hydrated also. You can teach your doggies to drink out of your hydration pack by squirting water into their mouth. You can also carry a bottle specifically for them. My favorite is the H2O4K9. Just like you, it's better to give your doggies smaller sips of water more often.
So enjoy enjoy the outdoors this summer, and stay hydrated!