Yes, it is safe, but it’s often ineffective if you mix them in a bottle beforehand. Vinegar is an acid and baking soda is a base; when combined, they neutralize each other, essentially leaving you with “salty water.”

When to use them together: The “fizzing” reaction is only useful for mechanical agitation. Use the duo to unclog drains or scrub grout where the bubbling action can physically loosen grime. For most other cleaning, use them one after the other, not mixed together.