Was Ares associated with dogs? I heard in Sparta they sacrificed dogs to him for some reason (poor puppies D:)
Oh this is a good one and it is a bit complicated given that we have one mention yes on an offering of a puppy in some sort of chthonian night sacrifice outside of Sparta. That mention comes from Pausanias. However Pausanias mentions that the sacrifice happens to "Enyalios" (Ἐνυάλιος) The word on itself means "War-Like" and as a word appears already in the Iliad for example in rhapsody 17. But here's the thing; sometimes is seen as an epithet of Ares and sometimes it is seen as a different deity with some traditions (probably later ones) have him be a son of Ares instead. (In Iliad it mentions: Ἄρης δεινὸς ἐνυάλιος "Ares the dreadful warlike", so it seems more like an epithet there)
It is a bit more unclear whether Pausanias memorizes Ares himself by the word as his epithet or his son as a separate deity. We do know there was a worship of Ares in Laconia the same way that there is in many parts of Greece after all so it is not impossible that Pausanias is mentioning Ares himself there but on the other hand it could be a separate deity.
Either way yes, we do see a sacrifice of a puppy and more specifically (always according to Pausanias) at night before a fight, the youths would go to Phoebaeum, somewhere outside a city called Therapne in Lacconia, and offer one puppy each group to Enyalios and it seems that the most valiant of animals seems a suitable offering to the most valiant of gods. Pausanias mentions he knows only one more example of Greeks offering puppies and those would be the city of Colophon (a city in the area of Ionia, modern day Turkey) who would offer a black female dog to the goddesses "of the roads" (Ἐνόδια), usually as an epithet refers to chthonian deities like Hecate