Danny Trejo Slams Ex-MLB Star Adam Jones Over Ketchup Tacos, 'Nothing Worse'

Taco expert Danny Trejo is going OFF on Adam Jones for slathering his Cinco De Mayo treats in ketchup ... telling TMZ Sports that's THE WORST condiment a person can add to a taco!!

"You can do taco-anything," Trejo says, "but not ketchup!"

Jones -- a 5-time MLB All-Star -- posted a pic of his ground beef-ketchup delight on Tuesday ... celebrating the fifth of May while defending his choices for taco toppings.

"It’s my plate," Jones said. "I eat them how I want to. Ain’t a specific way. So gracias."

But, the owner of Trejo's Tacos -- a SUPER-popular taco joint in L.A. -- tells us Jones is dead wrong for putting Heinz anywhere near the tortillas!!

"The reality is that you can put anything on a taco," Trejo says, "but ketchup goes on a hot dog!"

In fact, Trejo says he's so appalled by the move ... if he saw the food crime go down in real life -- he'd buy the person's dinner just to make sure no ketchup touched the tacos!!