Experiences with the Steiner Variation 1.e4 e6 2.c4!? in French? How sound is 1.e4 e6 2.c4!?, the Steiner Variation in the French Defense, and would you actually recommend it? Does it work well in normal games, or is it more a surprise weapon for blitz?
It's undoubtedly sound in the sense that it does not by force lead to any sort of catastrophic disadvantage for White, but it offers very little if any objective possibility of obtaining a theoretical edge.

If you're specifically trying to reach an IQP position, it's probably preferable to play the Exchange Variation and only then follow up with c4, since Black has other reasonable options against c4 on move two besides an immediate d5 thrust. 2... c5, for example, can reach positions similar to those found in the Sicilian (i.e., various Maroczy Bind structures that crop up against the Kan, Taimanov, or Accelerated Dragon variations) and English Opening Hedgehog systems. That said, an immediate d5 seems to be the most popular response, and it's probably what one would typically expect from a French player (and what I would likely play myself).

It's certainly a viable way to play if you enjoy IQP positions and you want to avoid the well-trodden paths of main-line theory. It shouldn't lead to any advantage against correct play, however.