Walmart offers the Ozark Trail 20-oz. Double-Wall Vacuum-Sealed Tumbler in Orange for $5. Opt for in-store pickup to dodge the $5.99 shipping fee. That's $3 off and the lowest price we've seen for a single tumbler (we saw two for $7 in September, however). This BPA-free tumbler is double-walled and vacuum-sealed.

Note: It's available in a selection of other colors from a buck more.