The key to everything in life is being hydrated! I've passed out from dehydration on enough school trips to have learned that the hard way. Because of my history of ~thirst~ I always carry a water bottle with me and I've used quite a variety of different bottles. Here are my favorites that I'll always reach for when I'm heading out the door.
I first picked up a classic Nalgene from my college's bookstore and still use it all the time. I loved that I could hook it onto my backpack via the loop that keeps the cap in place, making it easy to take with me on the go. A friend of mine also swears by his splashguard insert that makes drinking from the Nalgene's wide mouth less prone to spillage. While I'm partial to the purple, Nalgene water bottles are available in a variety of fun colors!
My Camelbak water bottle is always my go-to. I've lost a handful in my time and always go out of my way to repurchase. I've even purchased the sippy-top part (officially known as a bite valve) since I've managed to knock those loose and into the dirt from time-to-time. The sippy-top and straw combo on Camelbak water bottles makes it a danger-free way to hydrate on the move. If you're walking, running, driving, lying down, or just focusing hard enough on something else that there's the risk of missing your mouth, the Camelbak bottle is the way to go without a doubt. Also, while I love the capacity of the Nalgene, my Camelbak fits more easily into the build in cup-holders on equipment at the gym. While I also have this bottle in purple, there are plenty of other colors too!
I inadvertently commandeered a friend of mine's Hydroflask this past summer after he left it at my house and I grabbed it on my way to work. This is the highest capacity water bottle I've ever used and I loved using it until my friend finally reclaimed his rightful ownership. It did an awesome job of keeping my water super cool and keeping me from collapsing in the middle of the tennis court during long days of working in the sun. Hydroflask has tons of top quality, customizable, insulated water bottles and other drink-ware that will fit any of your hydration needs.
This style of water bottle from Lifefactory is the only glass bottle I've used and overall the quality is great. I love the grippy material that wraps around the glass bottle and the lid always stays on super tight so it won't leak in a bag. I've also used this water bottle for bringing tea to class when I've run out of thermoses and have been pleasantly surprised by how little tea residue ends up lingering in this glass bottle after cleaning as compared to my experience putting non-water liquids in plastic bottles.
Side note: It always blows my mind how water bottles seem to go in and out of style. Remember how trendy Sigg water bottles were? At the end of the day all you need to do is find a vessel (or several...) that holds liquids and fits your lifestyle.