I’m not sure I would have known about “thickening” water except for my job. I don’t know where you purchase it, or what it costs .. or if your doctor has to write a prescription for it.
However, I hope it is something you can use to help you with your issue.
So far I’ve been lucky as I learned to sip fluids instead of a regular drinking mode, and to take pills more cautiously. Some of them are humongous and need broken in half where possible.
Now if I could just get stupid hospital dieticians or lab techs to understand I’m not allowed SOY products on liquid diets or for test. That Ensure is a NO go item it contains soy.