You can make oatmilk at home. Mix 100g of oats with 1l of (cold!) water, whizz in a blender, then strain through muslin or a fine sieve.
Compared to store bought oatmilk, it’ll have a bit of sediment that will slowly separate out, and you’ll have to mix back in. I expect commercially they’re able to blend and strain more thoroughly, and some brands might use additives to keep it homogenised.
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