Since the coconut milk I buy (Aroy-D, $3.99 for 1 L) is really thick and tends to get clumpy in the fridge, I tried transferring it to a 2 L wide-mouth mason jar and adding a litre of boiling water then stirring it until it was smooth. It separated a bit while it was in the fridge, but it didn’t clump. At this concentration, it’s nice instead of cream in coffee or blended into a smoothie.
Next, I’m going to try mixing coconut milk out of coconut cream concentrate. Based on comparing the nutritional information on coconut milk and on coconut cream concentrate, I think that 150 g of coconut cream concentrate should mix into a litre of coconut milk of a similar strength to the 1:1 coconut milk to water mixture. (At 99 cents per package of coconut cream, it’d be about half the price.)