USB lunch boxes are a gimmick. Get a 12V cooler instead.
Plugging a cooler into your car’s USB port won’t keep anything cold for hours — USB just doesn’t deliver enough power.
Most car USB ports put out 5 volts at 1–2 amps (5–10 watts). That’s fine for charging a phone, but thermoelectric coolers need 40–60 watts just to maintain a temperature difference. So a “USB mini fridge” either doesn’t exist in any useful form, or it’s a tiny 6-can bag that barely cools below ambient and drains your battery if left on.
If you actually want sandwiches and drinks safe for hours (below 40°F for cold), you have two good options:
A 12V thermoelectric cooler that plugs into the cigarette lighter port. Brands like Alpicool or RIGID work decently, especially if you pre-chill the food. They’re not powerful enough to freeze things, but they’ll hold a safe temp. Just remember they cool slowly and are noisy.
A decent passive cooler with ice packs — like a Yeti or a cheap RTIC. Pre-freeze the packs, pack everything cold, and it’ll outlast any USB gadget for hours of driving. This is honestly the best “road trip lunch box” for most people.
If you’re set on USB, you’re stuck either warming things (heated lunch boxes work fine on USB) or accepting lukewarm drinks. For food safety, skip the USB idea entirely.
Get a passive cooler with ice packs, or step up to a 12V plug. Future You’ll thank you at hour six.