Reanimando means "reviving" or "resuscitating". It's a dramatic and powerful word that you wouldn't normally expect to find in a pop song.
In "Copa Vacía," Shakira uses this medical term metaphorically to describe a failing relationship. She sings, "Reanimando un corazón que no reacciona" (Reviving a heart that doesn't react), creating a vivid image of her desperately trying to bring a love back to life that is already gone. It perfectly captures the feeling of trying to save something that can't be saved.
Have you ever felt like you're giving everything in a relationship and getting absolutely nothing back? That's exactly what Shakira is singing about in "Copa Vacía." She's completely fed up with a partner who is emotionally distant and always distracted. She complains he's "más frío que el mes de enero" (colder than the month of January) and too busy with work, telling him, "Te haría bien, mi amor, un poquito de ocio" (It would do you good, my love, a little leisure). The whole song is built around this powerful feeling of trying to get something that just isn't there, like "queriendo beber de una copa vacía" (wanting to drink from an empty cup).
But then Manuel Turizo comes in and tells a different story! He flips the blame right back at her, singing that she's the one who is cold and that her kisses are like saltwater—they only make him thirstier. He feels like he's trying to revive a heart that won't react. It's a classic case of two people in a relationship who both feel neglected and unloved, each pointing the finger at the other. They're both thirsty for affection, but neither can seem to quench the other's thirst.