Rod holders can be made many different ways. The most cost effective way is to get some 2" PVC from home depot and cut it into 4-5ft pieces. Cut at angles to make it easier for the PVC to go into the sand. I use 1" angle iron and duct tape wrap it to the iron. I use a hammer to bang my rod holders in the ground. Vehicle mounted rod holders are also a nice option. I have a front and rear rod holders that insert into trailer hitches. My final beach set up includes a mixture of all of the above.
I prefer to use high visibility duct tape (neon yellow or neon orange) for oncoming traffic to see. I also use reflective tape on my rod holders and fishing rods. No one has smashed into my rods yet but I'm sure it will happen sooner or later.
"Look how goofy my Jeep looks with all these rods all over the place. I should take a pic."
These are probably 10 years old. They are pretty beat up looking but they work well
A friend of mine made this for me. The holders slide in for when you're driving down the street