Methanol is a variant of alcohol, just like ethanol. But while ethanol is the principal alcohol found in drinks such as vodka, methanol is highly toxic.
In the human body methanol breaks down first into formaldehyde and then into formic acid and its salts.
Less than a teaspoon of methanol is enough to cause blindness.
Kidney failure, brain damage and death are some of the outcomes for Australian travellers who have suffered methanol poisoning.
In many parts of Asia the tax on alcohol is high. To produce a cheaper drink some bars will substitute locally fermented arak.
In Bali a 600ml plastic bag of arak costs less than $2.
It is not uncommon for arak to contain dangerous amounts of methanol.
Methanol can be accidentally produced during a fermentation process intended to produce ethanol, for example if the temperature during fermentation is too high, or if the brewer is not experienced enough to flush off the first part of the distillate, which will contain most of any methanol that has been produced.
It is unlikely that you would be served arak in the bar of a decent hotel, but far more likely in a bar advertising $5 cocktails.
Both ethanol and methanol look the same, colourless and with a slight chemical odour.
A simple test is to burn the spirit in a teaspoon or other small metal container.
If it burns with a blue flame it's ethanol, clear or yellow like a candle flame means methanol.
Ask the barman for the spirit straight from the bottle, if it's diluted with a mixer it won't burn.
Safer still, stick to beer.