It might be a UX thing more than a balance thing. It's hard to feel a 15% boost to Calli tosses, for instance, especially when your attempts don't last long enough to max anything, or even reach level 3 in anything. The occasional double soda is a bit easier to feel, since you can see the double sodas (even if you're twenty meters above them).
Maybe the upgrades just need "juice"? Something to make it feel like Calli's throwing you harder, like the upgrades are doing something?
Another point of technical feedback: Sometimes spacebar works instead of clicks and sometimes it doesn't? It works most of the times I load the game, but sometimes it doesn't. It's a small point (you're instructed to click, and clicking always seems to work), but it's also really weird.
(Browser version, same device each time.)