Combine tonic water, gin, water, lime juice, sugar and lime zest in a large pitcher or bowl. Divide among 6 popsicle molds and place lids/sticks on top. Freeze until solid, about 4 hours.
Any popsicle molds you have will work here, but we are digging the plastic, BPA-free ones that are super durable with soft, rounded edges which makes them kid-friendly (and let’s be honest, drunk adult-friendly).