This largely depends on your own tendency to get motion sick. The Drake Passage can get turbulent, but it is occasionally placid as a lake.
We highly recommend purchasing motion sickness medication in case the former occurs. If you find yourself without any such medication, we sell very effective brands on board.
There are also a number of best practices you can adopt should the seas get rough, such as avoiding alcohol, smoking, or any foods that are spicy, fatty, or have strong odors.
You can also keep to the lower decks of the vessel, where rocking will be less severe, fix your gaze on the horizon, or simply lie down. But not all of these remedies will work for everyone, so you have to decide what will help you based on your own experience.
We can recommend reading our blog: 7 tips to defeating motion sickness.