Dishwasher tablets are strongly caustic and most contain sodium hydroxide. This attacks aluminium, so I'd definitely not recommend using this in any engine with aluminium components anywhere in the cooling system. On a Panda, I'd expect this to destroy both the radiator and the heater matrix in short order, especially if run up to temperature, and it won't do the head much good either.
This might work on vehicles with an all-iron engine and a copper cored radiator.
I would be overly worried, although I have never tried it
It what garages use to do everyday with k series blown head gaskets, there are full aluminium block, head and radiator
We are talking about a 20g tablet with around 30% alkaline so about 6g in 4.6L
More concentrated, direct in a dishwasher, does a fine job of cleaning aluminium parts
Not my photos
It will strip anodised finishes though
Running plain water, with a blown head gasket will have caused a very acid coolant, not changing the coolant often enough is aften kills the thermostat washer
The fact is been run in plain water probably an indication there already a leak, that needs addressing first, the colour of the coolant, I can almost guarantee it's had k-seal or similar
Burping out is normally associated with air being sucked in and expanding