Start by getting an empty one-liter plastic bottle, some baking soda, and white vinegar. The bottle obviously must be empty.
Pour 150 grams of bicarbonate into the bottle, then gradually pour in 300 ml of vinegar. It is important to proceed slowly to avoid the effervescent reaction generated between the two ingredients causing the solution to escape from the bottle.
Pour the contents of the bottle down the drain, making sure everything fits. Squeeze the bottle to release the solution with light pressure.
The effervescent reaction will also continue in the drain, removing any residue and unblocking it.
Wait about 5 minutes, then pour plenty of hot water into the drain to eliminate all residues and have a perfectly functioning and scented drain.