In making my sea buckthorn juice, I used the sea buckthorn berries that were boiled for a short time. The recipe is in the profile (but you can also fill it up with the fresh berries).
This is then put into a 0.7 l bottle and added with the alcohol, the vanilla pod, which is cut open and scraped, and the sugar. Close it and let it stand in the window for 6 - 8 weeks and shake it every now and then so that the sugar dissolves, then strain and pour into another bottle.