Very little information. Sparkling-tailed Hummingbird is nectarivorous, and reportedly visits "a great variety of flowers" (Züchner 1999), but there is very little information about the plants that they visit. Edwards and Lea (1955) observed these hummingbird feeding on flowers of "thorny legumes". Also visits flowering Inga trees (Howell and Webb 1992).
Sparkling-tailed Hummingbird also consumes insects (Wagner 1946), as do most if not all species of hummingbirds (Remsen et al. 1986).