Alejandro,
When the group sits down to play, that's one of the questions that the MC should ask the vampire player: "Are you able to go out in the sunlight? If so, how?"
If the player isn't interested in addressing the whole sunlight threat, then ignore it. I've played games where the vampire was simply really pale and burned easily, so they didn't like hanging around in sunny places. I've also played games where if sunlight touched a vampire, they burst into flames.
The MC should ask the player how it works, and build on the answer.