A reader writes:

Two nights ago on the way home, a guy ran out into the highway in front of our bus, was hit and went under the wheels. We stopped and I and several others rushed back. He was... very... torn up (don't want to be graphic), but somehow he was still trying to breathe, so I know he was alive. While others with more first aid knowledge than I tried to help (but there was honestly no way, short of divine intervention in a spectacular miracle, that he would survive), I suddenly thought about how he may not be Baptized. Several cars had stopped by that time, but in the course of the little time I had all I could find was a McDonalds cup that had some diluted, warm coke in it. I used that as the water for the conditional Baptism and used the form I had learned ("If you be not Baptized, then I Baptize thee..." etc)

My question is this: I know that in emergencies anyone can validly Baptize, but when there is no pure water to be had, is using something like I did (flat diluted soda in this case) still valid? Was what I did valid at all?

I am reminded of the sage words of Mark Twain: "I was gratified to be able to answer promptly, 'I don't know.'". 

Here's what the Catechism says:

1239 The essential rite of the sacrament follows: Baptism properly speaking. It signifies and actually brings about death to sin and entry into the life of the Most Holy Trinity through configuration to the Paschal mystery of Christ. Baptism is performed in the most expressive way by triple immersion in the baptismal water. However, from ancient times it has also been able to be conferred by pouring the water three times over the candidate's head.

Of course, the Catechism doesn't define what "water" means and whether water with sugar, food coloring and a few other ingredients is valid matter.  That's because the Catechism is not written with such remote and unforeseen circumstances in mind.  It neither allows nor forbids what my reader did.  it's just silent.

What we do see, from very early on is a certain flexibility in the Tradition in accommodating various circumstance.  The Didache, for instance, show a certain Middle Eastern flair for dickering:

7:1 Concerning baptism, you should baptize this way: After first explaining all things, baptize in the name of the Father, and of the Son, and of the Holy Spirit, in flowing water.

7:2 But if you have no running water, baptize in other water; and if you cannot do so in cold water, then in warm.

7:3 If you have very little, pour water three times on the head in the name of Father and Son and Holy Spirit.

Don't know what the author would say about sugar water, but my guess is that somewhere or other (God knoweth where) some sacramental theologian has taken up some analogous question.  If any of my readers knows, feel free to share.

For my part, I can’t help but think that the Church’s doctrine of ecclesia supplet (“The Church supplies”) matters here.  My reader did the best he could in a sincere attempt to do the will of God.  It seems to me that, in a Tradition where the unbaptized Good Thief can find salvation this, as well as something of the idea of the Baptism of Desire is at play here.  But that’s just my guess.  Whatever else is the case, it was nobly done and I trust that God heard your prayer and will answer it in whatever good fashion is best for the poor soul you were trying to help.

For me, the main thing to keep in mind when pondering cases such as this is to remember that sacraments are given by Christ as sure encounters with his grace, not as the only possible hope of encounteing grace and certain not as reducing valves intended to keep as many people as possible from his grace.  So while considerations of valid matter are serious and should be reckoned with, we should also be cautious about assuming that God plays "Simon Peter says" ("Oops!  You didn't happen to have any water with you, so no grace for that guy!").  As Holy Church herself points out: "God has bound salvation to the sacrament of Baptism, but he himself is not bound by his sacraments" (CCC 1257).

Meantime, if it's possible (and it may not be since I assume the reader has no idea how to find this person again) the person should, in an ideal world, be conditionally baptized, just to make sure.

Well done, reader.  You did your best!