Score the vanilla pod lengthwise and scrape out the pulp. Mix oat drink, coconut milk, vanilla pulp, sugar, 1⁄2 tsp. salt and baking soda in a pot. Bring to the boil, reduce heat and simmer 1 1⁄2 for 2 hours at low heat.
Stir about every 15 minutes.
As soon as the mass is reduced by a little more than half, remove the pot from the heat. Pour into hot-rinsed twist-off glasses, close and chill. Keeps for 5-7 days in the refrigerator.