Crystal Light, for example, has drink mix packets that contain flavored powder for you to mix with water. Why are these better? Because every time you make a glass or pitcher of tea, juice, etc. from these, you are eliminating the use of the plastic gallon bottles that manufacturers use to package the drink.
All you have to do is buy a nice pitcher that you can reuse to make drinks. It will also save you money to mix your own drinks because the drink mix packets and cheaper than buying a gallon of juice or tea on its own. You reduce your carbon footprint by using less packaging AND you save money.
Drink mixes also come in To Go styles that you can add to your water bottle for your convenience. Not your plastic water bottle, but your reusable bottle, right?