1) Find a birch tree (harvesting the birch sap is time specific i.e. the first warm weeks of spring thaw – when the temperature is about 10C in March-April time – when the birch trees wake up from the winter sleep and then the birch trees can be juice for about couple of weeks). The juice flows best during day – midday – especially when it’s warm and on the warm, sunny side of the tree. 2) Cut the end of one of the branches (another way is to drill a hole in the tree and attach a plastic tube or make a cut in V or Y shapes on the birch tree and attach a bottle underneath). 3) Attach a plastic bottle to that branch. 4) Wait until it fills in with birch juice (depending on the birch tree it might take a few hours or overnight to fill in the bottle). 5) Drink the birch water or you can freeze it as ice cubes.n freeze it as ice cubes.