There's a command to fill the bottles from the fountain. I think it's either [capital] 'H' or [capital] 'F.' I forgot which one. But, there is a definite way of filling the bottles and IDing them. You can quaff, which is risky, by using 'q'
Saw your post on my TOME dump. I'm potion scumming Erebor with empty bottles, not drinking them without knowing what they are, so I get to see if it's Corruption or some other nasty thing before I drink. Do you know how to do that? If not, it's a great thing to know, especially handy for stocking up on healing and other buffs before taking on a big fight, and Erebor is a great place to do it, with the quadruple fountains and deep levels for good potions.