If you do happen to find yourself
We added some fresh lime juice, and topped it off with club soda made from Scarlet's Sodastream, but I would suggest just buying real club soda because Sodastreams don't actually make anything bubbly.
I might also add some mint next time. Or swap the lime for muddled bluebrries. Or, if I lived in Washington still, I'd go outside and pick some blackberries off the vine and use them instead of watermelon.
The possibilities are literally endless, because it's called a ______ gin fizz with, so as long as you have gin and fizz and something to fill the blank, you're doing it right. So, I guess I never really made this drink properly, since we had no fizz. Sodastream. Psh.