Wow, clearly the fact that the Sonoff sends 24v DC and the solenoids are AC does not make a difference? Anybody who is a fundi in AC vs DC for solenoids comment? Just want to make sure I buy the right stuff.
Clearly you don't understand how the Sonoff 4CH Pro works.
But don't worry, I'll help you out a little.
My Sonoff is powered by 220V AC. It can also be powered by DC, but don't let that confuse you as I didn't use that. See the below picture for reference:

The outputs are called "relays", they work like a fancy switch. There are 4 of them, and they're labelled on the Sonoff like this:

Looks a little complicated, but the simple version is that the "relay" can either turn off something that's usually on, or turn on something that's usually off. I use the latter as I want my sprinkler to be off by default.
Now the really cool thing about a "relay" is you can choose the parameters of voltage and current that you want it to switch. You don't have to rely on the power source of the Sonoff itself. Thus, if you want 12V DC, then that's the power source you should wire up through your relay to your device.
I opted for a 24V
AC Orbit sprinkler power supply as that's what my solenoids need to work. I wired it up as I previously described in an earlier post.
And, as if by magic, when my Sonoff switches on the "relay", the power from the power supply makes its way to the solenoid and my sprinklers turn on.
Good luck with your sprinklers - hope you get your fundi advice and buy the right stuff.
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PPS Don't get snotty when you're the one who is wrong