unflavored (adj.)

• dead
• dilute
• diluted
• flat
• flavorless
• inane
• indifferent
• insipid
• jejune
• mild
• pulpy
• sapless
• savorless
• stale
• tasteless
• thin
• unsavory
• vapid
• washy
• watered
• watery
• weak
• wishy-washy