The working theory is that Luffy used people's laughter, celebration and wishes for fuel down in the fire festival. Mostly because it can be taken as a form of prayer/ritual that could be utilized by Luffy.
This is because his fruit's name is the Sun God, and until now we haven't seen why it's a God and not a Warrior or something else.
To sum it up, the more people laugh, do the drumbeat, wish for their own happiness, the longer he can fight. That may even be why they tried to snuff out everything about the void century and Nika, because belief is power for him.
I can definitely see Luffy being powered by the alliance instead of food EOS.
This is because his fruit's name is the Sun God, and until now we haven't seen why it's a God and not a Warrior or something else.
To sum it up, the more people laugh, do the drumbeat, wish for their own happiness, the longer he can fight. That may even be why they tried to snuff out everything about the void century and Nika, because belief is power for him.
I can definitely see Luffy being powered by the alliance instead of food EOS.