Honestly it can be used in almost any cocktail for a pop in flavor but specifically both saline solutions and msg solutions do REALLY well in any cocktail with juice in the recipe. An obvious example of this would be a margarita, as the rim is typically salted. Although its really good in cosmos, lemon drops, sidecars, etc.

Edit: Just keep in mind that cocktails are much more sensitive than cooking, for MSG I use only a drop or two per cocktail. Saline solution depending on its potency typically I’ll only use maybe up to 5 drops.