Actually, there were 2 types of Fleet Phoso-Soda. Ginger- lemon flavor, (green box) and unflavored(blue box)
Despite what everybody said, and no matter how much you chilled it, the ginger-lemon flavor was just nasty.
It is arguably worse than the cherry flavored magnesium citrate, though the cherry citrate is harder to keep down.
The only way I ever found of getting the ginger-lemon flavor down was to hold a stadium cup of water in one hand, the phoso-soda in the other, kneel down in front of the toilet, start with a sip of water, then a small sip of Phoso-Soda then a large sip of water, then count to 10 and repeat. When the phoso soda is all down.continue to kneel there for 5 minutes to make sure it stays that way. When you get up, don't get dressed, don't do anything physically strenuous, drink plenty of water, and don't get too far from the toilet. It should start to have it's effect in 45-90 minutes.
The unflavored was just very salty. Go to the salt you cook with, lick your finger, and put a coating of salt on your finger, then lick it off. That gives you an idea what the unflavored tasted like. Sometimes I could not get the unflavored, but when I could, that was what I preferred. I had gotten in the habit of taking it as above by the time I discovered the unflavored.
Normally I used it as the last stage of a system cleanout. The unflavored was also the first oral laxative I ever used without an enema.The only other one has been Dulcolax.
Given that the unflavored stayed down OK, I might take a Fleet Enema orally, but given the difficulty keeping the ginger-lemon flavor down, plus the fact that the Fleet Enema is not buffered for oral use makes me skeptical. If the issue was how hard it is on the kidneys, then the buffering of the Phoso soda should slow things down enough to at least partially mitigate that issue
That said, it would be a tough call. Especially since Epsom Salt can be taken orally and tastes no worse than the ginger-lemon flavored Phoso Soda.