The mixture of alcohol with fruit juice and soda: Cocktails are one of the most desired drinks on vacations and functions.  If you desire to drink cocktails while on a keto diet, it makes no harm to your ketosis.

Normally when on a keto diet, it is recommended to consume only low carb foods and drinks. It gives a stretch to have drinks that are not sugar-sweetened. Thus Some of the alcohol varieties are keto-friendly.

Alcoholic drinks will not have any major effects on ketosis as long as the drinks are no-carb. Pure alcohol like vodka, whiskey, gin, brandy among others tends to have no carbs in them which makes them keto-friendly. 

So Cocktails are fine as long it a non-carb alcohol is mixed with keto-friendly fruit juice or diet soda. Cocktails like Lime mojito and coconut lime martini are just some examples.

Even though cocktails do no harm to your ketosis, some people tend to get addicted to drinks while on a keto diet. So always have a limited amount of drinks.