One good source of energy for the brain is lactate in fermented milk products. Lactate is the primary source of energy for the neurons, mostly supplied by astrocytes.
Please take a look at this articles:
https://www.sciencedaily.com/releases/2014/02/140211084053.htm
https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/s12986-022-00687-z
