Question

How could you tell whether a liquid is honey or vinegar?

Answer 1

Based on the liquids viscosity (which is a measure of how quickly/slowly a fluid can flow).

Higher viscosity represents a "thicker" liquid & slower flow (honey)
Lower viscosity represents a "thinner" liquid & quicker flow (vinegar)

Answer 2

I really don't recommend identifying substances by taste, but honey is sweet,

while vinegar is sour.  A safer way would be to see if one is more viscous

than the other.  Viscosity is the ability to pour a fluid.  This is a topic in fluid

dynamics.  Hydrodynamics and aerodynamics are sub-specialties.