I will give my roommate 20 sets of two shots, one with diet coke and one with coke zero. This market will resolve YES if he can correctly guess which shot glass has the diet coke in at least 17 out of the 20 sets.

Context and useful other info:

My roommate has expressed that he is willing to wager up to $100 that he is able to pass this challenge.

I will not bet in this market.