Water should be by your side at all times, literally!
Most people do not drink nearly enough water.
Lack of water (dehydration) is very often confused with hunger, so people reach for food when what their bodies really want is a huge glass of water.
The old saying "drink 8 glasses of water a day" is rather vague, I mean, how big are those glasses?
If you want to know how much water you need to drink, take your body weight (in pounds) and multiply it by .55 and that's exactly how many ounces of water you should have in a day.
If you are an extremely active marathoner (most of us are not) you can up that by multiplying your body weight by .65.
Your water should be consumed throughout the day, not all in the morning, or chugged at three meals only, but sipped on all day long.
This means frequent trips to the bathroom, but less trips to the refrigerator.
I carry this jug with me everywhere, I like it because it is Bisphenol A (BPA) free and has a sippy top with a cover. It holds a half gallon so I aim for one and a half of these, I know that's a bit more, but that works for me. The large one gallon jugs are difficult for me to drink from, but whatever works for you!
I actually panic if I am out and about and don't have a big reserve of water in the car with me. I even keep it by my side on my way home from work in case I am stuck in traffic.
The reusable containers are more ecologically sound, as they don't fill up the land fills, but be sure to clean it out regularly so you don't get sick from bacteria build up!