Check out this Route 6 Location guide for Pokemon Sword and Shield. This includes Wild Pokemon spawns including Sizzlipede, found TM & TR, item guide, trainers, map, and more!!!
You can find Sizzlipede within the grass of Route 3. They don't appear outside of the grass. When you see an exclamation point in the grass, go to there and you might have a chance of meeting a Sizzlipede.