Found this on quora but reddit wont let me post the link

Being instantly water soluble, you can collect the residue: just run a small amount of water down into the stem with your finger covering the bubble hole, then swirl that water around in the bubble. You’ll see all of the white dissolve instantly. The brownish marks will partially dissolve, which is the portion that is still unburnt, usable methamphetamine. You’ll now have a water infusion that can be drank straight from the stem. Alternatively you can pour it into a container to evaporate, but this is tedious and may compromise the yield. Most people I knew drank it and had a chaser on hand becuase the tiny amount of liquid is concentrated and would taste awful.