Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

Here's an idea:

If you possess the Brew Potion feat, I believe that anytime that you drink a potion you should be able to "Recycle" the empty potion bottle.

Use a potion? Get an empty Potion bottle after it's used.

Don't wanna fill up your inventory too quick: Make it so that it can be toggled.

Remember, kids: Reduce, reuse, recycle!!!

....or....

Just add a "broken glass" sound effect once you drink a potion, showing that the bottle isn't reusable.

well it takes an action to use a potion and a free action to toss the bottle... you really gonna use another action to store a 99ct. bottle while an orc is swinging an axe at you?

also there is no way to tell the difference between a potion and a grenade with brew potion spells because they all act like wand charges, so you are talking about a lot of work filtering spells...

If I were maschistic enough I'd do that with some off chance of mixed effects from the remains of the last potion (but for now just buy new ones and consider old ones soiled beyond redemption ).