Brief Answer:
It's due to excess fluoride ingestion.

Detailed Answer:
Hi xxxxxxxxx,
Thanks for the query through health care magic platform.I have read it & understand your concern,
soapy taste to anything you eat... indicates excess ingestion of Sodium Fluoride. which is a toxic substance..
* common possible source of fluoride-
- It is used in very small amount as cleaning & foaming agent in things routinely used by us like tooth paste/ mouth washes ( for oral hygiene)
- It is also used in materials for dental treatment
-Tap water can have excess fluoride (natural ingredient rocks in earth from where water is acquired )
- Fluoride is also used in metallurgy / pesticides .. so being in contact of these can raise increased ingestion of fluorides.
- Food articles like cake mixtures, dry milk powder, backing powder may get contaminated with sodium fluoride
* Too much ingestion of fluoride may cause fluoride poisoning. Poisoning is characterized by diarrhea/ vomiting which may lead to shock, dilated pupils & cause serious health problem.
It's good just a soapy taste all the time warns you to be alert & take care to eliminate the nasty salt from your use/ get your self examined medically & exclude severe effect.
* Fluoride poisoning can be diagnosed by testing of gastric washing/ vomitus
* Management consists of eliminating fluoride ingestion & treatment ot poisoning if need.
- Personal level - This can be achieved personally by stopping use of tap water/ changing tooth paste/ Use hot saline water for mouth washes/ avoiding fluoride treatment in dental clinic/ Be careful while handing pesticides
- If you have any of the symptoms of poisoning.. you should go to ER, get investigated & taken exert advise & treatment from a toxicologist
I hope the answer is both useful & informative to you. Any follow up query is welcome.
I request to grade the answer if you find it useful .. before you close the query.
Thanks.

---