ATM you can buy 420mL Portable Electrolytic Hydrogen-rich Water Cup for $18.99 (in Banggood). Price history, coupons and price alert are available on this page. What is the best price?
420ML Portable Electrolytic Hydrogen-rich Water Cup Hydrogen Rich Water Cup Electric Hydrogen Rich Water Generator Bottle Quality Filter Titanium Portable Antioxidant Lonizer
Latest price update (UTC time):
Banggood ($18.99)
Banggood warehouse is located in China. Low/high price? Current price is the lowest in history (according to CouponsFromChina database)! I found coupon for you. Check this out.
Link: Banggood product page
Price without coupon: $22.99
1. ($18.99): BGAnnivHG01
coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop.
This is the best price ever noted in my database!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGb4f63a
(these codes were not working in latest coupon update, but you can check them out anyway)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for 420mL Portable Electrolytic Hydrogen-rich Water Cup is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).