In FUT, SBC Fodders refers to high-rated player cards that are not much valuable in the game or in the Transfer Market at the time, but can be consumed in a SBC due to their higher rating or their card types. In other words, these cards are useful mostly because users can use them to "feed" them into SBCs rather than play with them in matches or trade them in the market.
One of the most important attributes for FUT cards is the Pace attribute. Usually, players with high OVR rating but low pace are considered as SBC fodders are they don't have much value to be on the field or be traded in the market. Another factor that makes a player card SBC fodder could the player's nationality and/or league which makes the player difficult in having a higher chemistry with other players in the team.