What is the word in English for Gandairiyan (Urdu), that is, small pieces of sugarcane, as can be seen in these photos:
There is no single word I know of in English that has the specific meaning of this Urdu word.
People use many strategies to describe this food. I think the variety in how people describe these shows that there is no established word for them in English. For example, they may be called "slices" as in the caption to this picture: "Sugar cane slices (a.k.a gandarian)." Someone else called them "sugarcane cutlets."
Also see this comment from this forum post: "I reckon ganderian are probably one of those few things that are not readily available outside of Pakistan" and the explanation in this Daily Delhi blog post "ganderian (गंडेरीयां / Sugarcane cut into bite size." If you need to be specific when talking to an English speaker about this food, I would just use the Urdu word and then explain what it means like this.
"Billets" is the term actually used for the cut small pieces of the actual large sugarcane plant itself with the rind (outer covering) intact/unpeeled. Smaller bite-size peeled (rind removed) pieces Do Not have a specific dictionary name in the English Language. For explaining the "URDU term GANDERI (singular) or GANDERIAN (plural)" various terminology may be used and variation of it depends upon the speaker. It may therefore be concluded that reference to the said term may be made as small Pieces, Slice, Chunk, Bite or Cutlets of cane and any other appropriate term.
Billets are the cut small pieces of cane. Gandarian are the small peeled (rind removed) pieces and hence may not be called small pieces of cane.
Billets Common name for chopped lengths of cane (approx. 300 mm) produced by mechanical cane harvesters. - Canegrowers
During harvest, the cane harvester drives along each row and cuts the cane stalk off at the bottom of the plant. The long stalk is then cut into many shorter lengths called ‘billets’ (around 30cm). Another machine known as a cane haulout drives alongside the harvester, collecting all the billets. - Canegrowers
Google chunks of sugarcane and see the image results.
a thick piece of something