We have enjoyed this homemade version for years. It is a perfect cool down when it is hot. Just don't sip it too fast :)
Recipe from: Mostly Homemade Mom
1 packet Kool Aid (any flavor but cherry is our favorite)
2 cups seltzer or club soda (I use club soda)
1/2 cup sugar
2 1/2 cups ice
Dissolve sugar and kool aid packet in one cup of the club soda, you can do this right in the blender. Add ice and pulse until all ice chunks are gone. Add remaining one cup of club soda and blend. Pour into glasses and serve.