Use it to experiment with a couple gallons of hard apple cider if you haven't before. That much yeast should be enough to ferment 2 to 2.5 gallons. Just pick up some apple juice the next time you're at the grocery store. You can use Motts or the store brand as long as it doesn't contain any preservatives that would kill the yeast. Ascorbic Acid is ok it's just vitamin C. If you have a fermenter that small, awesome. Sanitize it, oxygenate and pitch. If not, just pour a few cups out of the gallon to make headspace and chuck the yeast in. Put the cap back on, but only tighten it down about halfway so C02 can escape. Give it a couple weeks and bam, you have hard cider. Once it's fermented you can bottle it up and drink it still, you can add priming sugar and drink it carbed, you can add some splenda to sweeten it a bit and then carb it and drink it. It's really easy and you'll get a pretty good product with minimal work involved.