But... are the sheep OK?
See, this is why being experienced enough to take proper precautions
is clearly a good thing!
This is actually something I've given a lot of thought . . . the whole consensual/accidental vore survival tropes thing.
The science geek in me knows there's a reason that this specific example (and several similar ones) would be a pretty bad idea.
You know what the active ingredient in Tums is? Calcium carbonate. You know what happens to carbonates (or bicarbonates) when they react with acids (aside from neutralizing it)? Lots of CO2 (carbon dioxide) gets released. (ever seen vinegar with baking soda?)
CO2 is heavier than air, so will tend to concentrate and displace air on lower portions of a contained space (or room, for that matter). It would not only displace a lot of (whatever remaining) air there was, but the increased CO2 levels themselves can cause other problems, even if there's enough breathable oxygen left. http://en.wikipedia.org/wiki/Hypercapnia
(most notably the psychological panic response to elevated CO2 levels)
Now, there's a very common viable alternative available that totally avoids those problems, and it's typical commercial form has some other bonuses for making such an . . . experience
It's probably obvious to any other science/chemistry geeks around here, and I'm tempted to detail it right now, but I have my reasons for holding back. (this is already on the verge of being spoiler as it is :p )
Oh, and a related, but totally non-spoiler-relevant note: acids aren't the nastiest stuff in gastric juices found in the stomach . . . it's the enzymes that do most of the real work (the hydrochloric acid in most/all mammals -and most other animals- is pretty dilute, really), but the acid is a powerful catalyst for many of those enzymes, so neutralizing it would indeed largely render the enzymes passive as well. (more so if the pH was actually pushed beyond neutral, and into the slightly basic/alkaline range)
And that's not getting into how difference species have different sets and concentrations of enzymes actually present, most extreme would be true herbivores vs obligate carnivores -like all Felids. (anything in-between -preferential carnivores, like most canids, or true omnivores- would vary in-between somewhat, both in content and concentration)