You can put the drink in either hand or hold luggage. If you want to drink straight away, put the drink in your carry on luggage, as it can be a while before your suitcases are delivered to your cabin.
Your bags will be scanned, but the security staff are looking for guns, knives etc, not fluids, so no problem with alcohol, perfumes, shampoo etc. Much different to airport security.
Also, just to point out that the security staff have no interest whatsoever in the P&O one litre per person alcohol limit rule !
We put bottles in hand luggage, wine boxes in suitcases.