Despite having sidled slowly past many sloths whispering outrageous things about their mothers in the days since I found out about the badge, I've yet to have a single one spit at me.
@jiva: yep, there's an upgrade card for that, I have it and it's called "Friend of Metal: By purchasing this upgrade, you confirm your allegiance to Metal. In appreciation (or perhaps disgust), Sloths will occasionally spit Snails down at you when you walk past their trees."...
So far, I seem to get spit at around 3 times per trip through sloth lands at 2 snails/spit...don't know if there's a card that boosts the amount of snails spit, or the numbers of times being spat at...if so, I've yet to come across it!
Feed the slot until it goes back into his tree (sometimes it works after feeding less than full, after about 5 feedings)
Keep moving under the tree, standing still did not seem to trigger it for me.
The sloth will stick his head out and look around.
If it is the sloth that spits he will usually do so the 2nd time he sticks his head out so just keep moving under that tree.
This worked for me every single time once I found which sloth will spit at me on a street. (Don't have the badge yet though as I ran out of metal rods plus it's pretty boring)
I tried the same thing but without feeding while walking through other sloth streets, sometimes it worked, sometimes it didn't. Worth he try though.
Opening the game under a sloth seems to work fairly often, only one sloth spit per st, only got one spit per 10 mins, sloths often spit after you're done feeding them - not sure if happened if already spit at on that st, tp to under sloths, walk back and forth under them a few times.