I found a simple recipe for fizzing bath soaps. I plan to put them in the kids stockings, they love LUSH bath bombs but they cost $7 a piece (per bath)!!!! These don't fizz as nicely but the kids will still have fun with them.
1/4 cup of finely crushed Epsom salt mixed with 1 cup of baking soda mixed together well, then spray with 1 tsp lemon juice, 1/4 cup water and any scent you like till it looks like damp sand that will stick together. A scent is not required, I added a little bit of vanilla. Then I let them dry over night. I had to let the molds dry for 2 days and still most of them fell apart. The cookie cutter ones turned out best.
I need to search for some other soaps and bath fizz products for the kids.