A useful item you’re going to encounter in your travels in Pokémon Sword and Shield is Exp candies. These are going to provide your Pokémon with small boosts to their experience pools, meaning you won’t have to grind out levels in battles so much.
The best way to acquire these candies is straightforward. All you have to do is complete Dynamax battles in the Wild Area. You first encounter this area on the way to Motostoke, and the battles are held at the glowing red dens. Walk up to them to face a Dynamax Pokémon with three other trainers, or some NPCs.
After completing the battle, you’re going to receive a few Exp candies based on the difficulty of the fight. The harder the battle and the stronger the Pokémon was in your encounter, the more and high-quality candies you’re going to receive.
Feel free to venture around the Wild Areas grabbing all of the Exp Candies you can find. You can save these candies to use on a Pokémon you want to level up faster than having them in your party and gaining Exp from the shared party XP.