I'm going to copy my post from the main HK sub to here, so hopefully more people see it:

Tow straps, anyone?

I've always wondered what would happen if you hooked up a 2"x20' tow strap while these vehicles were stopped or moving slowly past a roadside tree. These straps usually have an ultimate break strength of 17,000 lbs, so there's no way they're getting away if caught at a standstill and the strap is attached to something springy, like a tree.

Some of these riot vehicles still have their stock recovery points, but attaching a strap to the cage armor they use on their water cannon/UNIMOG trucks would do a helluva' lot of damage if they were to drive away.

Alternatively, with a large enough tow strap, like a 6"x30' tied to concrete blocks or something or parked vehicles or something, you could effectively trap one of these riot trucks and/or block off a street. The strap can hold 60,000lbs, and a significantly heavy weight at the end would absorb the energy of an impact well.

It's like how they stop the AT-AT's in Star Wars... but with offroad recovery straps!

The HK Police's UNIMOG has some weak points as well. A tow strap could be attached to anything circled in yellow, and a tree, or some other heavy object on the side of the road. If the snorkel circled in red could somehow be blocked, the engine would receive no oxygen and stall. Due to the purpose of a snorkel (water fording) it makes sense that this is the only air intake for the engine.

Alternatively...

...you could always climb on top like this dude in Chile! High risk, high reward though. With a crowbar, you could likely break into some access panels. If not, a battery-powered angle grinder would definitely do the job.

Additionally, there are two access hatches on each side. I don't know what's in there, but a Moltov thrown in there would have good ventilation to combust, but it would be difficult to put out because of the louvered shutters. You'd be effectively using their own design against them.

Some other important points...

• The tactical vehicle (?) is a Mercedes UNIMOG 437.
  
• The water cannon trucks are likely Mercedes Actros 4/New Actros
  
• The HK Police's UNIMOG uses Michelin XZL/X-Force tires. These are tough but NOT run flat. A large enough puncture and they would deflate beyond a point where the central tire inflation system could NOT maintain pressure.
  
• Not sure what tires the water cannon vehicles use, but likely similar tires.
  
• However, these tires may include run-flat addons.
  
• It may be possible to throw a fishing net over the watercannons, which would entangle them and prevent them from moving. If two people approached the vehicle from either side with a net attached to tall poles, and laid the net over the watercannons, this might work. Best to weigh down each corner of the net with a brick.
  
• Putting sugar or salt in a gas or diesel tank will NOT BE EFFECTIVE. Water or sand may be effective.
  
• Water may be most effective; both gasoline and diesel float on water. Enough water in a fuel tank and the engine could hydrolock or starve.
  
• Sand may clog the fuel filter, thus starving the engine.
  
• Some photos:
  
  
  • Water cannon schematics
    
  • Water cannon right/front
    
  • Water cannon left/rear/partial interior
    
  • Water cannon front closeup
    
  • Water cannon chassis/drivetrain (best I could fine was a scale model of the MB Actros).
    
  • UNIMOG left/front
    
  • UNIMOG snorkel closeup
    
  • UNIMOG drivetrain
    
    Hopefully some of you find this helpful. Trying to do what I can from halfway across the world! Stay strong, Hong Kong!