Espetinho literally translates to "little skewer" or "kebab". It's a common street food in Brazil, often grilled meat on a stick.
In the song, the singer contrasts his humble offering of an "espetinho" and a ride in his old car with a rival's ability to provide luxury. He argues that true love doesn't need to be bought, making "espetinho" a symbol of authentic affection over material wealth.
This song is about being the poorer man in a love triangle, and finding out that money was never the thing that mattered.
The first verses lay out the comparison in very concrete terms. The other guy gets the VIP box while the singer is down in the crowd. The other guy has an unlimited card while the singer's card keeps getting declined. The other guy drives a brand new car while the singer drives one from 2004. He asks himself how he is supposed to compete with any of that.
Then the answer arrives, and it is the whole point of the song. The other man can hand her the entire world, but nobody ever asked her whether she wanted it. She would rather ride around in the little Gol, eat a skewer at a street stall, and be with someone whose affection costs nothing.
The chorus is where the title lands. An espetinho is a cheap grilled meat skewer sold on the street, the most ordinary night out you can have in Brazil, and here it stands for a relationship that is honest instead of expensive. His closing line says it plainly: he has his own worth, and he does not need to buy her love.