Try emptying your hands, put AK on shoulder, double click the handguard to be removed. It should move to your hands.

Its not just PET bottles. I first got sick from eating rice I looted from a friend who committed suicide because he couldn't cure this "whatever" it is. I the rice got me sick AND infected wounds (important to note that there is 2 things going on at once). I finally threw away the rice and stashed my stuff, and killed my self to clear it up. When I got back to my stuff, drinking from my canteen re-infected me. "Whatever" this is, can be spread.

Vomiting cures the SICK, but does not cure the infected wounds. Alcohol tincture will cure the infected wounds with 1 dose. Drinking/eating from a PET bottle, Canteen, cooking pot, bag of rice or box of cereal... basically any edible item that was previously used by you or someone else while sick will spread the sickness.

Once cured, emptying a tainted container onto the ground will bug your display to remove Energized and Hydrated and replace it with SICK. Logging out and back in will fix this, since you're not infected from actually drinking it.

Some of the food and drink you looted from your previous character is tainted or bugged. Ditch all of your canteens/PET bottles/cooking pots, and food items that can be used multiple times, like Rice and cereal.

Additional Details: Water containers that have become infected or corrupted (not sure what else to call it) will re-infect the player despite empty/refill cycles and water purification tabs. Additionally, just emptying a corrupted container on the ground will trigger a UI bug that shows your status as "Sick" and removes hydrated and energized status but does not appear to actually infect the player. Logging out and in fixes this UI bug.

Update 2: Food/water items are getting tainted with some mystery disease that's causes "infected wounds". Forcing vomiting cures the "Sick" status and alcohol tincture fixes the infected wound. Ditching all water containers, Rice, cereal, and fruit prevented re-infection. Infected items looted off my corpse by other players made them sick too. Tried using disinfectant spray on known culprit PET Bottle, caused visual bugs replacing my "Energized" and "Hydrated" with "sick", forcing an HUD update by overeating until "stuffed" cleared the display bug... no text messages indicated itchy wounds or other ailments. Not sure what this disease is, I dumped out all water, and refilled from well, and used purification tabs... but PET bottle was still infectious.

Got sick from eating rice, caused infected wounds. Buddy didn't believe me, so he ate the rice too, he also got "Sick" status and "Your wounds are itchy". Powering through all 4 stages until your wounds feel clean does not make the "sick" go away... and sooner or later, drinking/eating anything will cause infected wounds all over again.

Update: I packed all my gear into a Barrel, and suicide to clear the sick. Played several hours just fine, sticking to newly found food and water. Worked my way back to barrel. Took PET bottle to pump, emptied bottle, refilled at pump, and used water purification tab. Drinking from PET bottle caused instant SICK and "Your wounds are itchy".