Secret Service agents were exhausted from lack of food, lack of sleep and then showed up on Nov 22, 1963 still drunk from partying the night before

I think this was a part of the assassination plan, to get the SS guys exhausted on the day before.  They had little if any food or drink the whole day on November 21, 1963.  They went looking for food that night when they finally got to Ft. Worth. They heard about this place "The Cellar." They went there.
They drank Everclear.  This brand name is never mentioned in the story of the drinking at The Cellar.
It's damn near 100% alcohol.

They partied until 5 or 6 a.m. when they had to be on duty at 7:00 a.m.

The Dallas Morning News revisits this.