About the thirsty guards, the one you give the tea to shares it with the other guards and that's how it makes all of them not thirsty.
I forget if it was in Unova or Kalos, but there's one place where a guard says "Sorry, there's something up ahead and you can't pass".
Also, related to what you said about the Wailmer training grunt, most grunt-related roadblocks. I'm always like "Why can't I just battle them? I do any other time." I see it more often in fangames than the main games I think, but it's happened a few times in the main series. Like the two Lake of Rage grunts who make you pay a fee. It's like the player just lets themself be extorted, when we should be perfectly capable of kicking their asses. It would be one thing if the grunts are in disguise and pretending to be officers or rangers, but when they're out in the open, there's almost never a reason I see that we can't fight them. The only legitimate one I can think of is in the Aqua/Magma hideout where they say the boss isn't there, which would make it a waste of time to search the hideout for him (it ended up being a waste of time anyway since he left with the sub before we reached him, lol).