Common soaking solutions recommend here are pedialyte soaks and honey soaks.
Pedialyte soaks are made using 1 part unflavored pedialyte to 10 parts warm dechlorinated water.
Honey soaks are made up of warm dechlorinated water mixed with 3 drops raw honey, followed by a soak in plain warm dechlorinated water to remove any honey left on the skin.

Pedialyte replaced lost nutrients and electrolytes in the frog, which will give it more energy and encourage feeding.
Honey soaks can act as an antibacterial and a laxative.