Can I drink the water that activated the heat packs?

No. The water used to activate the heat pack will boil, but you should not drink it. There are two layers; the polymer bottom pan contains the heat pack and activation water and then the stainless steel pan goes over it.  You can heat water in the stainless steel pan, and use the water from the stainless steel pan to make coffee, tea, etc. The water in the stainless steel pan will be hot enough to make drinks, but it will not boil.