Skyward Pride is the closest fit on the game's own numbers: Sayu's kit multiplies ATK, and a weapon is ranked here on whether its ascension stat and its passive act on that stat. The Unforged, "Ultimate Overlord's Mega Magic Sword" and Wolf's Gravestone come next. No playtested ranking has been imported for Sayu, so this is arithmetic over the kit data rather than a damage measurement.
Run Desert Pavilion Chronicle on Sayu, with Viridescent Venerer and Song of Days Past behind it. Main stats are ATK% sands, ATK% goblet, Healing Bonus circlet. Roll substats in the order Energy Recharge > ATK% > CRIT Rate > CRIT DMG.
Talent priority is Elemental Burst > Elemental Skill > Normal Attack. The Elemental Burst costs 80 energy, which is what an Energy Recharge target has to clear.
The strongest team is Xiao, Chongyun, Zhongli and Sayu, built around Sayu: Anemo · Swirl.