Mr. Whoopee

Mr. Whoopee is a panel van converted into a food truck. If you tap the horn button quickly you can turn the ice cream jingle on and off.

More info:
gta.wikia.com/wiki/Mr_Whoopee
https://www.grandtheftwiki.com/Mr_Whoopee

Hotdog

The Hotdog is a huge rear-wheel drive van turned into a food truck.

There are numerous spawns near roadside attractions.

It looks sort of like a camper on steroids.

 

More info:
gta.wikia.com/wiki/Hotdog_(Vehicle)
gta.wikia.com/wiki/Hot_Dog_Van