When I was updating this page, then coupon price was $22.99 for 420mL Portable Electrolytic Hydrogen-rich Water Cup (in Banggood). Basically copy coupon, view price history or create e-mail price alert. Best price?
Latest coupon and price update (UTC):
420ML Portable Electrolytic Hydrogen-rich Water Cup Hydrogen Rich Water Cup Electric Hydrogen Rich Water Generator Bottle Quality Filter Titanium Portable Antioxidant Lonizer
Banggood ($22.99)
Banggood warehouse is located in China. There are no active coupons for this product, but the price is pretty low isn’t it? Is it good price? Hmmm, price is higher than average (which is $18.99 right now), so better set price alert down below…
Link: Banggood product page
Price: $22.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGb4f63a, BGAnnivHG01
(you can check these old coupons out, but these probably won’t work)
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)).