If you knew what the ratio of the rats weight to time and then compare with alongside a standard humans weight and you could find the time it would take to fully dissolve an entire corpse. That is if you have proper amount of Mountain Dew for it to work.
Since a rats average weight is around 1 pound and a humans average weight is around 137 pounds. (According to google) If a rat 1 pound to 30 days to dissolve, a human would be 137 pounds to 4110 days.
But this is probably far from true as you have to have surface area in account as larger objects would start to dissolve at a much larger rate than smaller ones, but there’s more to dissolve.
And I’m not that smart to figure out the exact time, and I’m too afraid to google how long would it take for a person to be completely dissolved in Mountain Dew.