The song is referring to taking a trip and the car is 'swervin' (swerving) off the bourbon, which means that it's not driving in a straight line because the driver is drunk. Based on the scene being described, I think that 'hit the dip', means to drive too fast over a dip in the road.
A 'dip' is a place where there is a depression in the road that goes all the way across the road. It might be a channel for water to flow across the road so it drains off. If you're going too fast and don't see the dip in time to slow down there's a disturbing jolt and a loud noise when the car drives into the dip.
To explain the symbolism of the metaphor, we sometimes say we 'hit a dip in the road' to mean that our life is difficult or uncomfortable at the moment, or something bad happens suddenly. The song talks about taking a risk. When the lyrics say, 'Fuck it' they mean that we're not going to worry about the consequences of what we're doing. We're taking a risk, living recklessly (driving drunk) and hoping nothing bad happens as a result.