What is Reddit's opinion of Reservoir & Bottle cleaner tablets (24 Tablets) | Water Bottle Cleaning Tablets Remove Stubborn Stains & Odors. Compatible with Hydration Bladders, Hydroflask, Camelbak, YETI, Thermos - Made in the USA?
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#225 in Water Bottles

I've used some tablets from amazon for my travel cup that was just abused when I went into hospital.

Otherwise you could try Milton sterilising tablets and then rinse thoroughly with boiling water.

I use these, but haven't had the courage to drink from the tank yet.

< $25

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< $50