In our field of work, we often go into dark places, and sometimes an open torch isn't an option. While these are not strictly potions, they are bottle-based solutions we've been known to employ.
One option is a large bottle of thick glass filled with clear water, in which the egg sack of a starlight fly is inserted while still soft. In the water, it grows solid quite rapidly. Once hard, it can easily crack against the side of the bottle, freeing the glowing nymphs inside and creating an obnoxious glow.
A trapped candlesprite will grow dim while it sleeps, but while awake, its flame gradually burns through the cork imprisoning it. Also, the bottle will get quite hot, posing a serious hazard.