What is the best treatment for a bulging disk in one's back that is causing sciatia?

Depends. Depends on ones pain tolerance and whether serious neurological signs or symptoms are present. Anything from otc meds to narcotics to oral steroids to physical therapy to epidural steroid injection to discectomy or other more or less invasive surgery.
Lots of options. Sciatica can be managed effectively and can be relieved in a vast majority of people, but it will always require diligence on your part for nsaids, exercise, stretching and weight control/loss. For those still having issues it may require treatments (injections, surgery, etc) to maintain relief as well.
Integrative care. A herniated disc can cause back pain as well as foot pain by physically pressing on the nerves that travel to the foot and by irritating them through the extrusion of pro-inflammatory disc materials. Physical therapy and other conservative measures, including medication management, are considered first line treatment. If these fail, your physician may recommend epidural steroid injections.