Add water to bottom of a slow cooker. Add in ribs. Note: Ribs may need to be cut into small pieces depending on size of slow cooker. Cut between bones.
Cover ribs with onions and garlic. Add 1 ½ cups of BBQ sauce to slow cooker, saving ½ cup for later.
Cook ribs for 4-5 hours on high power or 6-8 hours on low power.
Gently remove ribs from slow cooker and place onto a foil-lined and greased baking sheet. Brush on remaining BBQ sauce.
Set oven to broil and broil for 3-5 minutes or until BBQ sauce begins to bubble and caramelize.