I've hauled many things with my 5... a yard of soil, a yard of mulch, 1/4 yard of small river rock, multiple dump runs, tree prunings, etc...
How did I do it? First, it does not go inside the 5... well, some of it can depending on what you're hauling of course, dirt, rock, mulch and especially compost do not go inside... also, don't think a yard of anything would fit inside the 5 unless you did 5 runs. I have a small (5 x 4) utility trailer I picked up a couple years ago for $300. It only fits a half yard (soil, mulch) at a time... and did those trips in two runs. Couple of things to think about... a yard is a lot of weight and much more "product" than you might realize, like you would have to line the entire back of your 5 because it would fill it up. Last year, I used a friends truck to haul a yard of gravel and even his truck was on the edge of being overloaded (probably was).
So either of these options will work... 1. Might be a good time to find a small used utility trailer that you can keep using over the years and will follow from vehicle to vehicle (check Craigs list) for things like this + dump runs, camping, hauling various items, etc. But if you do this, be aware that even hauling half a yard is quite heavy and you'll want to ensure you choose the correct ball mount for the trailer to ensure the trailer is level, this is especially important with the 5 and heavy loads... the 5 is not a truck, be careful. 2. Rent a trailer... but, this might be tough as most trailer rentals need a two inch ball, if you have a hitch on your 5, you most likely have a 7/8ths ball. I have both, use the 7/8ths for my little trailer and the 2 inch for pulling 1500 lb tent trailer in the summer. 3. Rent a truck from u-haul for the day for $25.
Also, one other note... before I had the trailer, I brought home about a 1/4 yard of some rock by using a couple cheap plastic garbage cans from HD. Filled them about a 1/4 way while outside the 5, then put them inside and continued filling them via shovel, then did this a couple more times. The yard is only about 15 minutes from my house so that helps. But again, even doing it this way, the weight build up very quickly and it's better to move some of it out onto a third axel if you can. Also if you do this make sure you secure those cans so they don't do bad things during an emergency stop.