Pistearme is a colloquial and very common verb in Mexican Spanish, especially in the context of regional Mexican music like Grupo Firme's.
It means "to drink alcohol" or "to get drunk." In the song, the singer says, "Y pistearme mi derrota" (And drink away my defeat), expressing his intention to drown his sorrows and forget his heartbreak by drinking.
"Entre Botellas" is a heartbreak song from Grupo Firme, featuring Pipe Bueno. The singer is drowning his sorrows after being left by someone he stayed faithful to.
He opens by refusing to be treated as a toy any longer, even though he was honest and got abandoned anyway. He admits he loved her like a fool and gave his heart to someone who, it turns out, only wanted him for what he could offer.
The chorus is the emotional core of the song: between bottles, drunk, he can't even remember, except he clearly can't forget either. Drinking blurs the pain of missing her and still wanting her, even while he tries to convince himself he's moved on.
In the cantinas he's dropped his pride, shouting into the wind that he still wishes he could be hers, right before catching himself and remembering how badly she treated him, and drinking again to try to forget for good.
Midway through, Pipe Bueno gets a shoutout, and the song opens into a celebration of the two artists and their countries, Colombia and Mexico, a joyful moment inside a song about heartbreak that is typical of the genre.