I cannot think that the sound you will get from that sort of set up would be even close to usable. Guitars really need a guitar amp or the correct impedance matched pre amp to achieve any semblance of tone.
You might as well plug into the 1/8" jack as to use a generic audio driver usb cable.
Solutions are many but none will be $25. Possibly as low as $40 however..
Firstly, It's important to have ASIO drivers for what ever it is your trying to use. Sonar ( and any DAW) will not perform well on a PC working outside of the ASIO environment. Sure it might sound OK, but then you'll find your timing offset is out of sync. Sound quality is good, but it does not sync up with the rest of the project.
Many people just work this way without even realizing it is happening. They right it off as they must have just played it that way and oh well. Sonar does a pretty good job of adjusting for offset in ASIO mode, but it is almost always off in all other modes. Try it with your interface. Do a loop back test in ASIO , then switch to WDM.
So your back to simply using a proper ASIO audio interface no matter what. My recommendation is to keep your eye out for a sale on a very basic interface that has at least an instrument input. I've seen Tascam's on sale for as low as $40 on MF Stupid Deals.
But I think I'd pick up a Focusrite Scarlet Solo because they have better drivers. $100.
http://www.sweetwater.com/store/detail/ScarlettSolo