To find a Gin and Tonic and Special Ingredients in The Bowels of the Beast in South Park go to the front left of the main room and pick up the gin and tonic:
Then go into the private room. Throw a Snap N Pops at the propane tank and go next to it and ignite it to cause an explosion:
Pick up the special ingredient on the floor. Then go into the room at the back left part of the room. Move the ladder near the fridge at the back wall:
Throw Snap N Pops at the glowing part of the cupboard and walk up the plank and pick up the special ingredient.