I couldn't find a single drawstring backpack tutorial that I liked, so I just made my own. It is fully lined and I used grommets to attach the drawstring (so it is adjustable in size). This is a gift for my nephew for Christmas. I plan on making another one in the future for my son, so I will have to do a step-by-step tutorial then. This was done on a whim and it turned out wonderful.
I chose the sports fabric because my nephew is an absolute sports nut, so I thought it would be fitting. Boy fabrics are hard to come by (that aren't baby boy fabrics). If you know of any good places to get boy fabrics at a reasonable price, please let me know. I have found some recently, but with having two boys, I see myself going through them quickly.