The drink that Captain Silver drinks to restore his power is a "genki drink" or energy drink. They are sold in Japan. You drink them and they perk you up. They can contain different things like turmeric or caffeine.
When Black and Silver are in a bar they are drinking a whiskey called "Johnny Winter".
Black, Red and Purle go to a bar/restaurant called "Naku-Naku" which means "Cry-Cry" in Japanese. You will notice lots of people crying. The joke here is that there is a nationwide bar/restaurant in Japan called "Wara-Wara" which means "Laugh-Laugh".
Each of the Eight Rangers has some background history that makes each one special. Red is a recovering alcoholic. Yellow is an unpopular aspiring rock star, Orange is a recluse who is addicted to online shopping, Blue is overly obsessed with the colour blue. Green is into Kagoshima prefecture, speaking with an accent of that area. Purple is a shy guy who loves a girl. The leader, Black, is an indebted gambler who was abandoned by his father.