This is a sexual act usually done by oneself. Ideally, it is done in a desert environment after eating spicy food yet can be done anywhere. After having a bowel movement, wipe some of the fecal matter over your testicles, then lie outside on your back with legs spread. The fecal matter will attract flies which shall land and 'dance' on your testicles thus causes a tingly or arousing sensation.
After I had some really spicy Mexican food, I wiped the other way once and speared my boys, then lied outside with my legs spread a little. The flies came right away and jumped all over it. They gave me the best Mexican Sack Dance ever.
Similar to a sack tap but it occurs during anal sex.
It involves several men linked by their penis and ass in a circle. When the man at the back thrusts vigourously, his sack strikes the sack of the man in front, who in turn "sack taps" the next. This then continues around the circle in a wave.
The mexican sack lunch is making use of your condoms in more ways then one. After ejaculating in a proflactic during anal penetracion tie it off carefully so not to spill. Take the tied up condom and give it to a friend so they may savor the love at another date. No refridgeration nessesary.
"Dude that mexican chick we met last night gave me an awesome mexican hacky sack before she went down on me"
"Maria started her intimate night with her husband off right by whipping out the salsa and giving him a mexican hacky sack as foreplay"