How did the horses get the joints and bottles in their mouths anyway? Don't even ask how they're supposed to skin up or use a lighter.
One explanation could be that they used matches, from a book instead of a box, and used their lips and teeth to use them to light the "drugs". They may have gotten the generic smokable drugs from another horse, but that leaves the question of where that horse got them. As for the beers, they don't have the same sort of incisors as a human, but maybe they pried them open with their teeth?
Page 13 specifically mentions Latawnya having the beer and drugs slapped "out of her hoof" by her sister, suggesting she's holding them as if she had hands. That and other parts (for example, Latawnya's parents hugging her at the end of the book) seem to suggest that the characters were meant to be Funny Animals instead of Talking Animals, but the illustrator didn't get the memo.
Twist-off bottle caps - one horse holds the cap in their teeth while another twists the bottle with theirs.