Is it permissible to trade in bee honey that has been fed only on sugar solutions, and is it permissible to sell honey that was purchased as authentic to customers with the same description without being completely sure of its authenticity?

First: There is no harm in trading honey fed with sugary solutions, provided its true nature is disclosed to the buyer; because concealing this is a forbidden deception.

Second: There is no harm in selling the honey you bought as natural and sold as such, as long as it does not become apparent to you otherwise. If it becomes apparent that it is not natural, then its true nature must be disclosed.