Tallinn has many smaller and a couple of larger parks. On sunny days, it is a common sight to see people sitting on the grass to relax or chat. Some of them are drinking beer, but unfortunately that is not allowed. Police might not be as strict as in Riga, for example, but to avoid an unnecessary unpleasant experience, enjoy your beer or wine in a pub/restaurant or at your place of accomodation.
It is said that people in the park warn each other if policemen are coming, but better keep your hands of alcohol while being in public areas.
Well, boys and girls, this is the one - Saku beer, world famous in Estonia and Finland and the reason of existence of many a ferry company. Hordes of Fins drag boxes of this stuff home and save hundreds of euros per year from the price difference.
As a Belgian, I am rather spoiled and not easily satisfied. Saku is not bad though. Not exactly "world class", but a soft pils, and easily enjoyable.