Re-filling fresh water tank while I dry camping

The blue seven gallon plastic jug that is sold at Walmart can be fitted with a hose. Take out the valve in the cap and replace with a 3/4" pipe thread hose barb. Put on a short section of hose and insert in the fill hole, lift and pour. I would look for something to place the jug on so you don't have to hold it up.
That's about as cheep as you can get, and not spill half pouring into a funnel.