Cupet-CIMEX  stations:

"La Bujía"

Carretera Central y Cespedes

I recommend this one as the easiest to reach.
It also sells sandwiches and drinks to you can stock up before a trip.

“La Punta”
Carretera de Baconao,

km. 25, La Punta,
Santiago de Cuba

Oro Negro stations:

“Alturas de Quintero”
Carretera Central, km. 2,5,
Alturas de Quintero,

Santiago de Cuba

 “Trocha”
Ave. 24 de Febrero y Carretera del Morro,
Santiago de Cuba