Which sippy cups are genuinely leak-proof for a diaper bag?

Verified-purchase reviewers and high-trust subreddit threads most consistently call the Zak Designs Kelso line and Tommee Tippee insulated bottles drop- and leak-resistant, with the caveat that leaks usually trace back to a misseated gasket or a chewed straw. GROSMIMI also draws strong no-leak praise, though a few reviewers note it can leak once a toddler shakes it hard.