Technically "Enriche" is just purified water. But it's more than that. Enriche is purified, sterilized, and vitamin-fortified. It has to be, because it's the only thing that is safe for people to drink.
Ever since the Hamidon Wars, people were terrified about the food they ate and the beverages they drank. The spores from the Devouring Earth were so prevalent in the years just prior to the Global Evacuation that just about everything could contaminate the public. Even food that was canned wasn't safe.
So when the sonic barrier was first erected in First Ward, emphasis moved to finding a way to purify water that people can drink. A process was developed and later perfected in Neuropolis that would remove the water of any contamination. The water was drinkable again.
Then the decision was made to add to this process. Man did not drink of water alone, so they added things to the water to help man. Just like fluoride was originally added to public water supplies in the 1950's, so too did the people of the newly-formed Enriche Bottling Company add "good" things to the water. Vitamins and other "additives" were included to help people be strong and resistant to the spores. One of those "additives" ended up being nanites, which help the masses deal with "troubling thoughts".
Not long after its introduction, Enriche became the number one beverage in Praetoria. This was mostly because all other forms of drink were made illegal until they could likewise be "purified".
People have Enriche with their coffee. They drink carbonated Enriche for lunch. They drink minted Enriche in frozen Enriche ice cubes. And even when other forms of drink (specifically alcohol) could be purified, they served it with Enriche or in Enriche ice cubes.
When people from "Statesman's World" began visiting Praetoria (in secret, of course) and they drank Enriche before returning to their home worlds, they discovered that Enriche had a combustible reaction when mixed with Crey Cola. Scientists discovered that both drinks have nanites in them, and that those nanites treated each other as a threat. The result was mutual assured destruction for the nanites, and an almost certain death for human host.
This is why officials in both universes say that you should not, under any circumstance, consume Crey Cola if you have ever consumed Enriche.
(See its Paragon Wiki entry for more information.)
In "Furia and the Guardians" #1, new immigrants to the Primal Universe are required to see a video of a Praetorian spontaneously combusting because they drank Crey Cola. This is something that Furia Powers had to see every time she to go the indoctrination process.