You need to be a Twitch Prime member, but you get this benefit if you have Prime.
Use code TWITCHCON when ordering.
These threads often devolve into arguments about tipping. I know arguments on the internet change my mind all the time, but let's not get into that.
The fine print:
Terms and Conditions
"Offer expires earlier of 11:59 p.m. (PT) October 23, 2017, or while supplies last. Offer applies to first-time customer orders. Offer is subject to the greater of (a) a minimum order of $10.01; or (b) the minimum order amount in your delivery area. Taxes, tips, and delivery fees do not apply when determining minimum order amount. Offer available to Amazon Prime Members and only applies to products purchased through Prime Now that are sold by Amazon. This offer does not apply to products sold by third party stores or restaurants that offer delivery through Prime Now. Offer does not apply to digital content, alcohol or to orders placed through voice shopping using Alexa, Amazon.com or any Amazon mobile application other than Prime Now. Items must be purchased in a single order and delivered at the same speed to a single address. Delivery fees and taxes may apply to the full value of discounted and free promotional items. Offer limited to one per customer and account. The maximum benefit you may receive from this offer is $10. Amazon reserves the right to modify or cancel the offer at any time. Offer is non-transferable and may not be resold. Offer discount will be allocated proportionally among all promotional items in your order. If any of the products or content related to this offer are returned, your refund will equal the amount you paid for the product or content, subject to applicable refund policies. If you violate any of these terms, the offer will be invalid. Unless an Amazon Gift Card is the stated benefit of the promotion, promotional codes (including those placed directly in accounts) may not be redeemed for Amazon Gift Cards."