Place potatoes into a large pot and cover with water; season water with salt and bring to a boil. Reduce heat to medium-low and simmer until potatoes are tender, about 20 minutes; drain. Put potatoes in a slow cooker.
Place bacon in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes.
Remove the bacon slices to a plate lined with paper towels. Crumble bacon and add to potatoes.
Return skillet to medium heat and reheat bacon drippings. Cook and stir sweet onions in the drippings until translucent, 5 to 7 minutes; add garlic and continue cooking until fragrant, 1 to 2 minutes more.
Pour onion mixture over the potatoes and bacon.
Stir vinegar, water, sugar, and salt together in a bowl; pour over the potato mixture. Stir potatoes gently to mix.
