I have fasted Taycie before and within 24 hours she is back to normal. I keep nutrical on hand and make sure she is drinking and staying hydrated. My vet also recommended fasting as well when her stomach is a mess.
One particular event I gave her 95% salmon with her dog food that morning for breakfast.Just a tablespoon. Well, It gave her the runs like I have never seen! It was awful

I ended up doing many butt baths that day, poor thing. I decided not to feed her that night and just let her tummy rest.
By the next morning she ate and all things were back to normal. Poop was back to normal and that was that. And, I threw the can of salmon out.. I am sure was glad