I used the calamansi juice cooler from Trader Joe's here. I suspect you could use fresh calamansi juice, that you've sweetened to taste. Or an alternate calamansi juice, but you're on your own a bit here. My advice if you're going rogue ;) - Fill half your glass with IPA beer, and then add calamansi juice/cooler/etc. until it tastes delicious to you.