Dobie is a naval term for wash. It is generally used with other words such as Dobie-dust or Dobie-powder meaning washing powder.
Instant-dobie is slang for deoderant or anti-perspirant as the act of putting deoderant on is joked to be a quick wash for 'stinky sailors' instead of them taking a shower.
hey dave, take a god damn shower instead of using the instant dobie. you stink of shit