Is the Hydro Flask Wide Mouth leak-proof?

Yes, with the Flex Cap screwed on tight. The cap has a silicone seal, so it can go in a backpack without leaking.

Does it keep drinks cold all day?

Yes. The double-wall vacuum insulation holds ice and cold drinks for many hours, and hot drinks stay warm for several.

Yes. The bottle and Flex Cap are dishwasher safe, though hand washing the cap extends the life of its seal.

No. The 40 fl oz wide mouth is too wide for most cup holders; the 32 fl oz is also wider than standard holders.

Capacity and size only. Both use the same wide-mouth threading and Flex Cap, so lids are interchangeable.

Yes. The 40 fl oz wide mouth usually sells for around $40 to $50 new, so $36 at Poshmark as of November 7, 2026 is near the low end.

Rated 4.6 out of 5 from 34 ratings.

9 stores we checked sell it, including eBay, Poshmark, Mainland Skate & Surf, Backcountry, Merchery.

At Poshmark, for $36.00, as of our latest check.

$36.00at PoshmarkObserved at 3:03 PM

Compared across 3 stores. Prices are checked against each store and labelled with when.