@kabutomania
 
They make bras for cows and stuff.
 
The joke is that Pinkie’s the only one there who fairly reliably appears with huge teats.

@kabutomania  
Yeah, but they’re not a Hands thing, so I don’t think Lyra would have it.  
Not sure who would have the hip-flask; Berry is usually depicted as a drunkard (though I prefer the ‘ponyville’s most prominent ‘berry-juice’ maker’ role (we all know it’s wine)) but it’s drunk on wine, and the occasional bit of cider.  
I can’t see her drinking anything strong enough to be worth carrying around in a small flask.
 
Though, actually… It could be innocent.  
Given the other items, it almost certainly is a booze bottle, but I figure Lyra could probably use a bottle of something to treat lyre-strings (or the frame, but the strings of any instruments seem to be their weak points)  
So it could be (though, again, almost certainly isn’t) a specialized oil for lyre-strings, or some such.
 
Otherwise, I figure anything from Berry carrying around some water to stay hydrated (she does probably drink at least as much as RD, even just from having to ‘sample’ her own wares to check if it’s any good - the question is more if she goes overboard or just sticks to that) to Pinkie having something weird.
 
Actually, nevermind, that last bit convinced me I know the solution:  
They’re all Pinkie’s!  
The pills, by the way, are vitamin pills; She needs to supplement her diet.  
And the ‘bong’ just blows bubbles.  
Why does she have a bra? To someday imply she’s getting dressed when the show-camera goes into her house.

@Lucky Shot  
bra’s are a human thing arent they?

For a bit I thought these were real…then I found this image.
 
BTW, is that Rick’s flask?

Pinkie’s the only one there who would need a bra, so…