Charlie Sheen -- Giving $1,000 to Waiter ... Who Got Stiffed By NFL Star

Charlie Sheen is taking sides in the "Tip War" involving NFL star LeSean McCoy -- claiming he's giving $1,000 to the waiter McCoy stiffed after a controversial lunch earlier this week.

Actually, it wasn't a technical "stiffing" -- the Philadelphia Eagles running back tipped a waiter named Rob 20 cents on a $61.56 meal at PYT restaurant in Philly. McCoy reportedly felt he was mistreated inside the restaurant.

The receipt -- with the 20 cent tip -- was later posted on social media by the owner of the restaurant, Tommy Up.

Now, Charlie Sheen is getting involved ... issuing a statement saying, "dear Tommy Up at PYT in Philly. Please tell Rob K I'm pledging 1000 dollars to him for the tip debacle just wanna help. c #NoJudgement"