[The Marching Mudokon]

I think that's the best explanation I've heard so far. Experimental purposes by the Vykkers make sense. Maybe they were doing some market research, and they might not just be for Munch, there could be other Oddworld species we don't know of that could use Aquabounce and etc. Just cause it had Munch's face on them doesn't mean it's just for him (outside of the game) it's just an easy way to identify the vending machines.