Are you talking about a big baseball cap with a dark brim and a white front panel with say, the stars and bars on it?
(Maybe that’s cuz I do most of my driving in the South and in Texas.)
Diesel fuel.
For the litte, and not-so-little, kids at home. Same for plastic model kits.
“Tire Thumpers”- 18-inch long heavy wooden cudgels for making sure their tires are seated on the rims properly, and breaking heads.
shotglasses with the state bird/motto/flower on them
license plate frames with NASCAR or other brilliant phrases on them
I see ‘em in the ladies’ rooms, too.
Jerky and Beef Sticks
Cigarette lighters in fanciful configurations
I’ve only been to two, but based on those, I’d say:
[ul]
[li]Porn[/li][li]Spittoons that clip on to your window or fit in the cup holder.[/li][/ul]
Yeah those also sell those butane ones, like the kind heroin users have.
And questionable egg salad sandwiches.
Comedy albums in the vein of Jeff Foxworthy, Larry the Cable Guy, etc.
Also, I don’t know if this is the still the case, but it seemed like for a few years truck stops were the only place where you could still buy brand new cassette tapes.
In addition to all of the above, they sell shelf stable packaged meals that are designed to place on the engine to be heated.
And the condoms that they sell in the women’s room tend to come in neon colors, or be ribbed, or are otherwise not your just plain old standard condom.
Little statues and figurines of angels, whimsical old people, children, or barnyard animals.
The really dedicated truck stops have artwork in this style.
Wallets on chains.
[ul]
[li]Blue Mountain greeting cards.[/li][li]Glurgey inspirational books and books on tape. Cassette tape.[/li][li]12 volt powered appliances: mini-fridges, hot pots, CRT-based TV-DVD combination units.[/li][li]State refrigerator magnets, thimbles, spoons and other trinkets.[/li][li]Blank log books.[/li][/ul]
Independent truck stops will often have a CB repair shop in an outbuilding, where CBs are modded, and export CB radios and linear amplifiers are sold.