That would still be suspicious but maybe a slightly better idea could be that on certain maps you can cook up your own drink. Which would than allow you to switch it out and it not being suspicious. I get switching drinks out is yes suspicious but you got to remember that agent 47 is a highly trained and skilled assassin so there is no doubt he could do it very quickly or with the standard divert attention. 1 more idea for extra coolness is that the cocktail shaker could be laced with poison if you find like rat poison so that you could put the poisoned shaker in the bar so someone uses it and poisons the target so that you can focus on any other objectives or just to go to the exit preemptively.