Slice open the vanilla beans and scrape out the vanilla seeds.
Add the vanilla beans, vanilla seeds, sugar, and water into a pot.
Bring the water to a boil, then let it simmer (no lid on) for 5-10 minutes. The sugar should have dissolved by now. The syrup will thicken in the fridge even more.
Pour the mixture through a nut milk bag if you want to get rid of the speckles or if you want to keep them you can pour it through a strainer. Then you can fill the syrup into a bottle and store it in the fridge forever.