Physicians no longer use/recommend oral benadryl much: too short lasting, needlessly sedating.
Much longer lasting, and much more potent (est. 10X more) antihistamines are cetirizine (Zyrtec), and levocetirizine (Xyzal).
Cetirizine and levocetirizine work well on an occasional basis.
That's two votes for Zertec. I'll get that in addition to the liquid Benadryl I already have.
Aspirin also is one of the quickest medicines to break down in storage: one of several where the manufacturers "expiration date" has some relation to reality.
One thing I know about aspirin is that it's expired when it smells like vinegar.
There is little data as to whether the expiration data on the two above liquid meds is real or not: an advantage of the tablet versions is that, except for aspirin, they seem to last for decades.
I'll focus more on tablets when it's an option.
Naproxen tablets, and others, can be put into a plastic bag, like a ziplock, crushed into powder with a hammer, then dissolved into the beverage of choice.
I have a pill crusher that I use every morning. It's nearly bombproof, made of thick plastic, and I have two spares just in case.