Orange Juice
So you have a growing family and a can of frozen orange juice for breakfast. A quick glance on the side of the can reveals the mixing instructions: Add 3 cans of cold water. Stir.
For all you Kentuckians out there, you have to empty the contents of the can into a pitcher first, you won't be able to add 3 cans of water to an already full can. Same goes for Kool-Aid. Two quarts of water won't fit in that itty bitty packet. 
Given my penchant for numbers and my kids penchant for fairness, reveals a disturbing problem.
The can of orange juice is 12 ounces. Adding three cans of cold water makes 48 ounces. A serving size is 8 ounces. There are only six servings of orange juice. Seven servings are needed.
Solution: add a fourth can of water. A little more quick math confirms that 60 ounces will fit in a half-gallon pitcher. The taste is hardly altered.
Bonus: 25% fewer calories per serving.
The other obvious solution is to use smaller cups. Yup, I do that too. And in following with my previous tightwad theme of reusing containers, from time to time Welch's grape jelly comes in fun kid-size character cups. I think the Pooh cups have all been broken, and we've got a some of Curious George cups and some Dragon Tails cups.
In my further quest for maximum tightwadedness, I noticed the frozen "grape juice drink" is only 20-30% juice... OK, what's the rest of it? Corn syrup. Then comparing prices and thinking about the orange juice lesson, I hit on an idea... if I buy 100% grape juice and thin it out, the kids will actually be getting more "juice" than if I buy the "drink." And thinned out with water, the cost is actually less than the "drink" mixed according to the instructions.
I've detemined that adding TWO extra cans of water makes only a noticeable difference in the flavor of the grape juice, but adds thee servings. It's now 66% juice, which is twice as much "juice" as the "drink".
Futher investigation shows the kids actually like the flavor of V8 Splash better when mixed half and half with water, and moves it toward the realm of affordability. Sunny Delight actually becomes a palatable drink when watered down in the same ratio.
And just for tuning in to my blog, here's a couple freebees: Do your ever find yourself chasing frozen chunks of orange juice around the pitcher trying to get it stirred? Try a potato masher. Also try this: a minute in the microwave on high with the top lid off. The metal on the bottom lid doesn't create any problems, but does get a little warm. Then add one can of water and stir (or mash) and then add the rest of the water. With less water it's easier to chase the chucks around. If you don't like the idea of the microwave, just use the potato masher before adding any water.