The source combines chilled espresso with Limoncello-flavored LaCroix and a little cream or milk. Here Limoncello refers to the sparkling-water flavor, not a requirement to add an alcoholic liqueur. The reviewer prefers a citrus-forward coffee with a smooth body and also discusses cold-brew concentrate as an alternative coffee base.
Build a small test serving first. Measure the chilled coffee, add sparkling water gently and finish with a modest amount of dairy if desired. Leave headspace for foaming. This sequence makes it easier to compare the balance without committing an entire can or large espresso serving to a mixture you have not tasted. A differently flavored sparkling water may change the result considerably.
Keep the proportions clear when comparing espresso with cold-brew concentrate, since their concentrations need not match. Taste before adding sweetener, and serve promptly while the carbonation remains lively. The source's creamy and lemon-like impressions are its own observations, not a guarantee that every coffee-dairy-sparkling-water combination will behave identically. The practical appeal is experimentation with a measured cold drink, without requiring a particular coffee subscription or commercial syrup.
The conversation
A good question can make a better brew.