While I totally applaud the effort, no one will use these vending machines with Dash. They may use the blockchain and Apple Pay or NFC, but never Dash. Why? 'Cos you have to buy Dash to spend Dash.
The driver here is the merchant, not the customer. The customer can simply use apple pay attached to a credit card because they don't see a cost associated with that. The Merchant on the other hand, sees 3-5% bank fees, chargebacks, disputes, delays in getting funds from the bank. DASH solves those problems for the Merchant.
It does, but the driver can only drive if there is an engine, and in this case that's the consumer.
A consumer will only consume if there is a necessity, or a problem solved.
If the merchant can sell a soda cheap enough for the hassle of the consumer to go out and buy Dash, bingo. Unfortunately, that is impossible right now. The actual Point of Sale makes it cheaper, but down the chain he'll have to convert to FIAT to keep his business alive. Add volatility, and the merchant is now a gambler. That is why BitPay et al. exist.
It's not viable for either at this moment. That, unfortunately, is the cold truth.