I wouldn't do anything crazy to your vehicle. Magnet at best. The guy I usually get firewood from started out of a s10 pickup. His advertisement is a magnet on the tail gait with just his number and "Firewood." Dude was able to quit his full time job and make more money just selling the firewood.
Mountain is right on about restaurants, but I'd say a heavier online presence will get you more business than anything else. There is one other option I'm not all for and I take issue with, but
a lot of people tend to go to church solely to promote their business. My church for example, like most, will only allow businesses owned by members of the church to promote. Obviously depending on the size of the church this can rake in some serious cash flow. Like I said though, I'm not all for it because a lot of hypocrites end up in the church that way. At the same point maybe they learn something while attending. I don't know, but it only takes an hour a Sunday. Tell you another perk, you'll definitely meet some preppers
Also check in with other small business owners like garages. A lot of the guys I know who own repair shops will promote for other businesses if they get some kind of perk out of it. Like 5% off or some kind of referral commission.
The biggest target you should have though is your local real estate agents. Make up some sort of "promotion" so home buyers can get a discount, free estimate, or other complimentary service. Some times you may even get simple maintenance jobs set up just to keep homes for market kept up for showing.
Hope some of that helps man, but I'll tell you above all else is customer feedback. Word of mouth travels far.