Various Jewish sources indicate the presence of Sadducees among the priesthood, including the position of Kohen Gadol. However, are there any Jewish sources that discuss Sadducees on the Great Sanhedrin? (I am wondering because of the Christian account in Acts 23:6-8. The description of the beliefs of the Sadducees matches with what we know about their beliefs from Jewish sources.)
There was a Tzeduki Sanhedrin in the times of Shimon ben Shatach, but he got them to disband, and the day this happened (28th of Teves) was declared a Yom Tov. (Megillas Taanis)
According to the Eshel Avraham there, this 'sanhedrin' of Tzedukim is mentioned in maseches Sanhedrin 52a, see Rashi at the end of the mishna.
This is also the 'sanhedrin' that was disbanded after the Chashmanim took power, mentioned in Megila taanis at the end of the fifth chapter. The mefarshim point out that this particular story is also mentioned Bava Basra 116b. There the protagonist is Yochanan ben Zakai.
(All these timings seem conflicting but the basic idea of Tzedukim running the Sanhedrin follows through.)