not sure about koolaid, but many commercial drinks have yeast/bacteria inhibitors in them.
if you're new to brewing, apple juice with no preservatives or liquid malt extract are probably the easiest ways to start up. liquid malt extract (LME) is what yeast crave basically. spending $20 on LME and an ounce of hops and listening to a homebrew store's advice will get you started really well.