Naruto fights Kaguya exhausting himself, while Sasuke sits in a desert sweating from the heat.
During the time period Naruto fights Kaguya before Sasuke helps seal her, after being useless vs
her the entire time aside from using ama saving him and Naruto, Naruto manages to use up all
his tailed beast chakra and is left with a small portion of nine tailed chakra.
The two confront each other and Sasuke gains all of the remaining tailed beast's chakra,
and uses a justu pumping every bit of chakra he had into it, leaving only enough chakra to use chidori, until he got more chakra from Kurama to use enton chidori.
The important part worth considering is Sasuke(with the beast) stalemated with Naruto after all of this: 200+ chapters ago before Vote2 Naruto claimed he had ran out of chakra vs Madara, atleast 3 days of war, he used up all the tailed beast, Kurama went low on chakra, and he lost his balls.