OK, the title's stupid.
I really like the Mio Flavored Water Enhancer ("Enhancer"? Really?), but I'm not particularly fond of the price or the flavor selections (I can't stand Fruit Punch and the last Strawberry Watermelon tasked like it was contaminated by the mold release used on the package). In looking at the package though, it seemed as if it could be reused if I only had something to put into it. It turns out that some of the flavor packets sold in my local grocery store work perfectly.
So, why go through all this in the first place? Well, there are a couple of reasons ...
First, I really like the convenience of the Mio squirt containers, but as I said, I'm not in love with the selection of flavors. And I like many of the flavors of the other available drink mixes (can you tell where I live from the product picture?) but they're intended to be made up in 16 oz quantities (small serving size) to 64 oz quantities (large serving size). I usually only want 8 oz. Furthermore, I generally don't like my drinks cloyingly sweet; I want just enough flavor to add some taste to my drink (I use about half of what the serving sizes call for). So a squeeze container of other flavors would be perfect.
This begs the question of why not just get a different container? Honestly, I probably could, but all the containers that were easily (and locally) available didn't have the handy seal that the Mio containers do (if you've used one, you know what I mean). There are probably containers that have a similar seal, but at a certain point it takes way too much effort to find them. And besides, I'm reusing a container instead of throwing it away. That's gotta count for something.
The second big reason is cost. One of these containers costs about $3.50 in my local grocery store. The two drink containers in the picture cost about $1.50 and $2.00 respectively and each will refill the repurposed Mio container three times (translated: it's MUCH cheaper).
So, how do we do re-purpose the container?
Step 1: Set Up
First, let's assemble our materials. We're going to need [at least] one of the Mio containers. The best way to get one is purchase it and proceed to enjoy the wonderful liquid water enhancement it provides. When it's empty, save it. Once you've got the container, you'll need to head to your local megamart and purchase a package of drink mix. My wife likes the Raspberry Lemonade, but I'm really partial to the Passion Fruit. Go with what you like. You'll also need a knife (to cut off the exterior label), a small container to mix the drink syrup in (mine's an old sterile specimen container that used to hold hops from when I homebrewed), and a whisk for stirring.
The drink containers in the picture (Raspberry Lemonade and Passion Fruit) has six packets each of which makes 8 cups. Each Mio container makes 24 cups. Theoretically, you could use 3 packets at a time and have exactly the same serving size. Personally, that doesn't work for me as there isn't enough water to dissolve the mix (and still stay under the capacity of the Mio container). Hopefully this will become clearer in a later step. Nonetheless, using two packets gives you a minimum of 16 servings, and in my case it's closer to 30 servings (like I said, I don't like it super sweet).
Step 2: Prep the Container
We'll start by cutting the exterior label off the empty Mio container. Fortunately, these are only shrink-wrapped plastic labels. If you can wedge the end of a paring knife under them, you can easily cut them off (be careful here and don't cut yourself).
Once the label's off, you'll need to take the lid of the container off to wash it out. Holding the container in both hands, gently twist the lid to the side (like in the picture) and then pop the top off. It'll be fairly resistant to coming off (naturally or it'd leak all over the place when the lid's on), but you should be able to get it off without resorting to larger implements of destruction or extensive use of your off-color vocabulary.
With the lid off, give the container a good rinse and then gently wash it out. I like to fill it with a couple drops of dish detergent and some water, put the lid back on, and then squirt it a few times to clean out the seal. After that, pry it back apart again and rinse the soapy water completely out.
Step 3: Prepare the Mix
Before we prepare the drink mix, we need to know how much this thing will hold. Filling it up with water and pouring the water out into a measuring device (in my case, the same container we'll mix in) indicates that we've got 2 fluid ounces to work with. Remember, this is an upper bound on how much it'll hold (more on this in a minute). Time to pour the water out and start mixing (note that you don't have to repeat this measurement ... as long as Mio doesn't change their packaging, 2 fl. oz. is the limit).
OK, with a now empty measuring container, open two of the drink mix packages and pour them into the container. Next, add very hot water (just off the boil) to about the 1.5 oz line. Using the whisk, stir like gangbusters. It will take a couple of minutes of stirring to get it all dissolved, and you may have to find something sharp to get the dry bits out of the bottom corners of the container. If it looks like it's not going to completely dissolve, you can add a bit more water but don't exceed a total of 2 oz. (or it's not gonna all fit in the Mio container).
My experience is that I've had to add a bit more water to get it to dissolve completely. I use very hot water (nearly boiling) to get it to dissolve, but even with that I still have to add a bit ... which is why I only use two envelopes as opposed to three. I don't think I could get all three to dissolve no matter how long I whisked.
Step 4: Fill the Container
Once you've got the drink mix completely dissolved in the water, slowly pour it into the clean, empty Mio container. If you're anything like me, you should be doing this over a sink where you'll catch spills (as opposed to catching h**l for staining the counter tops). Press the top cap back on until it seals and you're done (if you did the washing step like I did, you'll already know what the cap feels like when it seats).
Step 5: Enhancing Your Water
Use this [mostly] just like you used it to get the Mio syrup out. I say "mostly" because where you might pour a glass of water and then add the Mio, I find that it mixes and disperses better if you add the syrup first and then add the water. It's definitely more difficult to get just the right amount in there for your glass, but with a little experimentation you can tune it to your personal drinking preferences. Your mileage may vary.
Note that some of these flavors, when mixed in such a high concentration, result in colors that look like a Lisa Frank flashback. While it may be offensive to your eyes, it in no way hurts the taste (once it's diluted, of course).