USD is useless now, the government banks won't even take it anymore
CUC (Cuban Convertible Peso) was discontinued on January 1st, 2021, it is now useless in Cuba
CUP is now the only official currency, travelers can use it
CAD is accepted by all workers and businesses
It's possible to exchange CAD to CUP, but Cubans can exchange it themselves when they need to so it's best to use CAD instead
Cubans will offer a better exchange rate on CAD to CUP than the banks
Cubans can put CAD on their MLC cards (which are used at MLC stores, and apparently they're better to shop at than the CUP stores)
Coins are OK, but they can't get them exchanged, so they often ask Canadians to exchange coin for cash
Offer to exchange everyone's coins for your remaining cash on the last vacation day