If your sweat drop on the ball that is on his way to outside
 

of bounds, is it count as the sweat owner was the last that touch the ball? :D

I mean, what count as "touching". nail, hair, lace (shoes) ...?

Haha, how would you even see the sweat hit the ball?

Touching to me is seeing skin on ball or if the ball changes it's path/direction/spin in mid air even if I didn't actually see a touch. If the ball grazes a jersey I would say that is a touch also. Shoe lace? I think not. Hair? Yes.

Someone on this board will have an actual rule citation for you though.

What about shorts or socks? What if it hits a protruding jock strap (boys games only, I would hope)?

Coming from dairy country, I would say that it is the jerseys who graze. Of course, they were far outnumbered by the holsteins.

"Not by the hair of my chinny-chin-chin!"
 

2005-06 NFHS Basketball Rules Interpretations
SITUATION 9: A1 recovers a loose ball on the playing court near the sideline, with his/her body entirely in bounds. However, A1's head is hovering out of bounds and his/her hair (which is in a long ponytail) is touching the floor, out of bounds. RULING: A1 is called for the out-of-bounds violation. (7-1-1; 7-1-2; 9-3-1)