The band formed in 1998 by Raimund Marasigan (former drummer of Eraserheads) and Diego Castillo (The Aga Mulach Experience) for the purpose of fulfilling their mutual desire to work together. When Raimund Marasigan saw The Aga Muhlach Experience in a gig, He told to diego that he want to form a band that sounds like Weezer and Whales recruiting Diego Castillo and his band mates from The Aga Muhlach Experience consist of Mike Dizon (Teeth & Pedicab) to play drums and Myrene Academia (Imago & Duster) to handle bass duties. Sandwich was searching for a vocalist when music video director Marie Jamora recommended her friend Marc Abaya (Kjwan). A few years earlier, Marasigan was a judge at a contest where Marc Abaya jammed to a Beastie Boys song with his high-school band, Shirley Beans. Abaya then joined Sandwich. When Abaya and Marasigan met each other, they jammed together performing Beastie Boys "Sabotage" for 8 hours.
Although existing simultaneously with the Marasigan's foremost band at that time, Eraserheads, Sandwich provided a heavier, grittier sound, and built up their own fan base. Abaya was still in college at the time, and Marasigan would still tour occasionally with the Eraserheads, but these weren’t hindering factors for Sandwich, as there were many session musicians ready to take over in case of a member's absence.