https://www.serebii.net/news/2019/13-February-2019.shtml
It has been confirmed that the demo for the games Pokémon Let's Go, Pikachu! & Let's Go, Eevee! has been released on the Nintendo Switch eShop. This demo matches the demo that ran on tours late last year and comes in two versions: one for Pikachu and one for Eevee within one piece of software. It requires 2.2GB of space to download.