To get Dodge This, you need to be on Foundry as Assassin. You need to activate your streak and die from the molten steel that is being poured.

In order to get Holistic Medicine, you need to go to Siege Under (campaign) as Medic. Then, you need to head down to the elevator (but don't activate the override) and find the dead scientist. Crouch on him a few times and it should work.

To get Stick to Salad, you need to go to Caves as Tank. You need to find the flowing water and crouch on it (make sure you're fully covering it). Stay there for a bit and it should work.

To get Over Hydration, you need to go to Tropic as Commando (it's recommended to use the Wiggs skin from the explosive results achievement but it's possible without it). Head to the bottom, crouch and look down. Stay in that position for a while until you die.

To get "Why are you even touching this?", you need to roll a poop on the slot machine. Then you need to click it 1000 times. I would recommend using an auto-clicker.

(Thanks Rubikon05 for telling me how and helping me get this)
To get "It keeps it interesting" you need to get a kill with your primary, your secondary, during your killstreak, while in mid-air, and while sliding all in one life.