Apeche' is a slang conjugation of the verb apecharse, which means "to get emotionally attached" or "to get clingy". It's a unique word you won't find in a standard dictionary, often used in the Caribbean.
It's derived from the word pecho, meaning "chest", creating a vivid image of holding someone close to your heart. In the song, the singer warns his lover, "te dije que no te apeche'" ("I told you not to get attached"), defining their relationship as one that's purely physical, not emotional.
This song is all about a classic mismatch. Lil Naay lays out a situation where he's involved with a woman who wants a serious relationship, but he's made it crystal clear that's not what he's looking for. He's brutally honest from the start, telling her, "Yo le dije que yo soy muy bandido" (I told her I'm a real outlaw/player), but she doesn't seem to care. She's dreaming of running away with him, while he's just focused on the physical side of things.
The whole track is a back-and-forth between her desires and his. She says she's "falta de amor" (lacking love), and he bluntly replies that he's "falta de sexo" (lacking sex). He's not trying to trick her; in fact, he keeps repeating his position. When she starts talking about getting serious, he's just thinking about smoking: "Está hablando que me quiere pa' serio / Y yo voy por dos bluntes y medio" (She's talking about wanting me for something serious / And I'm on my second and a half blunt). He warns her directly that if she gets attached, it's going to end badly for her, saying "te va a dole' si te suelto" (it's going to hurt you if I let you go).