This blog is supposed to tell you which drinks and how many of that drink you can buy for below $20. The numbers I put before the drink are how many you can get of that item and that item only. 

List of drinks and how many you can purchase:

• 20 Happy Hour Beverages

• 6 Midnight Berry Freezes

• 6 Blue Raspberry Freezes

• 6 Wild Strawberry Freezes

• 6 Mountain Dew Baja Blast Freezes

• 20 Fountain Drinks

• 20 Pepsis

• 20 Diet Pepsis

• 20 Pepsi Zero Sugars

• 20 Mountain Dews

• 20 Mountain Dew Baja Blasts

• 20 Mountain Dew Baja Blasts Zero Sugar

• 20 Mountain Dew Quick Start Orange Citrus

• 20 Sierra Mists

• 20 G2 Gatorade Fruit Punches

• 20 Tropicana Pink Lemonades

• 20 Brisk Mango Fiestas

• 20 Lipton Unsweetened Iced Tea

• 12 Premium Hot Coffees

• 12 Regular Iced Coffees

• Unlimited Water

 All of the drinks are good deals but the best ones are the Fountain Drinks. The freezes were the most expensive. I didn’t count the water towards one of the best deals because the water is free.

https://www.businesswire.com/news/home/20140117005096/en/Taco-Bell®-Embarks-on-Largest-Expansion-of-Beverage-Menu-in-Company-History-with-Six-Unique-Flavors