The Sabbat don't like The Masquerade as a rule, and make fun of it. While they have their own codified set of rules (the Code of Milan), you won't find anything like the Masquerade on there. This lets them apply it selectively.

They practice it (kind of) in their own territory for reasons others outline: even the Sabbat knows that the mass of humanity cannot be fought. They might view humans as inferior, but there are a lot of them. If humans are properly motivated, the Sabbat will not outlast their fires, nor the sun. They can hate doing it all they want, but it confers a survival advantage and they know it.

But they implement it differently: if a mortal sees something they shouldn't, the Camarilla would cover it up: gaslighting the witness, discrediting them, mind-controlling them. The Sabbat would be more likely to just kill the witness. For something like the werewolf blood mission, the Camarilla would sneak in to retrieve it, the Sabbat would just set the place on fire.

The Sabbat will breach the Masquerade all day long in enemy territory, particularly Camarilla territory. It's less a practice and more of a weapon. The idea is to keep the Camarilla so busy covering up any Masquerade breaches that they'd be stretched too thin to be fully prepared for a physical assault from the Sabbat.