Take a piece of paper or card. fold it in half lengthways then width ways. Cut off 1mm from the corner which is made from the centre of the paper.
Hold three sides with one hand and one side with the other and pull apart. you should now have a makeshift funnel, you can tape the paper in this position but it is not
necessary (If you do not cut off the edge, you can use the funnel to catch any mess when drilling into a wall
etc you can substitute a paper towel for this purpose).
These funnels are very good for quick fixes but are not very good for prolonged use.
For prolonged use cut the top off any plastic bottles, cola bottles etc. If you have slightly more time small funnels can be made from tin cans, just cut off the top and bottom then fold the can to the desired shape- watch for sharp edges!!