It originally said "Level Up!" in the last panel, but then I heard "Power Up!" from the video game Altered Beast in my mind, and the rest was history.
I know it looks like she's just drinking from the same sippy cup potion over and over in this comic, but it is technically more than one. I considered various ways to indicate that the original potion had been used up after the first panel, but there were problems with every option I could think of.
Throwing the bottle away? Aside from not being very environmentally friendly, that's not very video-game-ish, is it? Plus, that littering aspect would have left me feeling compelled to give her a +1 to evil, which would imply a solution to that whole deal I wasn't intending.
Making a new bottle "poof" into her hand? Difficult to convey in a way that wouldn't be confusing except to someone who was already aware of what was happening. In short, it wouldn't have communicated what I wanted in a universal sense.
Have the potion fading away in panels two and four? Same issue as the previous one, really.
Ultimately, the real solution would be MORE PANELS! Which wasn't happening.
EDIT - Immediately got suggestions of having a pile of the sippy cups, which could work, but I don't like it in the context of a video game with an invisible inventory.
Specifically that context. Were I not being a nitpicky stickler for video-game-ishness, it would be the perfect suggestion.