She give me brain, research, and I prefer, reefer
The girl is giving him a brain (blowjob) Research >> Brain. Even though he is getting blowjob he prefer the Reefer, slang for Weed.
The phrase “And i prefer, reefer” also leads on to the next line, in that he prefers reefer to cocaine.
To help improve the meaning of these lyrics, visit "My Homies Still" by Lil Wayne (Ft. Big Sean) Lyrics and leave a comment on the lyrics box